Controlled semiconductor capacitors

• US 5,680,073 A
• Filed: 02/06/1995
• Issued: 10/21/1997
• Est. Priority Date: 06/08/1993
• Status: Expired due to Fees

• Current Assignee: Ramot University Authority For Applied Research and Industrial Development Limited
• Original Assignee: Ramot University Authority For Applied Research and Industrial Development Limited
• Inventors: Nathan, Menachem, Zolotarevski, Olga, Meyler, Boris, Ashkinazi, German, Zolotarevski, Leonid
• Primary Examiner(s): Callahan, Timothy P.
• Assistant Examiner(s): Lam, T. T.
• Application Number:
  US08/381,973
• Time in Patent Office: 988 Days
• Field of Search: 327/493, 327/498, 327/499, 327/500, 327/502-505, 327/568, 327/570, 327/571, 327/583-586
• US Class Current: 327/586
• CPC Class Codes: H01L 27/1443 with at least one potential jump or surface barrier
• CPC Class Codes: H01L 29/93 Variable capacitance diodes, e.g. varactors

Abstract

A controlled capacitor system, which includes a capacitor element (C1) and a forward-biased diode element (D2) connected in series with the capacitor element (C1). The system is such that the diode element (D2) has a capacitance which is less than the capacitance of the capacitance of the capacitor element (C1) when the diode element (D2) is under zero bias. The capacitance of the diode element (D2) is controlled by varying the forward current (I2) through the diode (D2). The forward current (I2) acting to control the capacitance of the diode element is selected such that the capacitance of the diode element (D2) is smaller than the capacitance of the capacitor element (C1) when the current (I2) through the diode element (D2) is below a minimum value. The capacitance of the diode element (D2) is bigger than the capacitance of the capacitor element (C1) when the current (I2) through the diode element (D2) exceeds a maximum value.

Claims

1. A current-controlled capacitor system, comprising:

(a) a capacitor element; and

(b) a diode element in series with said capacitor element, said diode element being a forward-biased GaAs PiN diode having a carrier concentration in the i-region of less than about 10¹² cm^-3, the system being further characterized in that;

(o) said forward-biased diode element conducts a forward current which acts to control the forward-bias diffusion capacitance of said diode element;

(i) said diode element has a capacitance which is less than the capacitance of said capacitor element when said diode element is under zero bias;

(ii) said diffusion capacitance of said diode element is controlled by varying said forward current through said diode element;

(iii) said forward current acting to control said diffusion capacitance of said diode element is selected such that the total capacitance, Cmin, of the current-controlled capacitor system is 1.1 times the zero-bias depletion capacitance, C_t (0), of said diode element at some minimum value of forward current, I_min ; and

,

(iv) the total capacitance, Cmax, of the current-controlled capacitor system is 0.9 times the capacitance, C₁, of said capacitor element at some greater value of forward current, I_max ;

wherein said capacitor element is a reverse-biased diode, having reverse-bias-voltage-dependent junction depletion capacitance, said reverse-biased diode thus serving the function of said capacitor element;

wherein said reverse-biased diode is a GaAs Schottky diode with contact to the N-layer which includes windows in said Schottky contact and said diode element is a GaAs P⁺ PiN diode, said reverse-biased diode and said diode element being integrally formed in a single crystal.

2. A current-controlled capacitor system, comprising:

(a) a capacitor element; and

(b) a diode element in series with said capacitor element, said diode element being a forward-biased GaAs PiN diode having a carrier concentration in the i-region of less than about 10¹² cm^-3, the system being further characterized in that;

(o) said forward-biased diode element conducts a forward current which acts to control the forward-bias diffusion capacitance of said diode element;

(i) said diode element has a capacitance which is less than the capacitance of said capacitor element when said diode element is under zero bias;

(ii) said diffusion capacitance of said diode element is controlled by varying said forward current through said diode element;

(iii) said forward current acting to control said diffusion capacitance of said diode element is selected such that the total capacitance, Cmin, of the current-controlled capacitor system is 1.1 times the zero-bias depletion capacitance, C_t (0), of said diode element at some minimum value of forward current, I_min ; and

,

(iv) the total capacitance, Cmax, of the current-controlled capacitor system is 0.9 times the capacitance, C₁, of said capacitor element at some greater value of forward current, I_max ;

wherein said capacitor element is a reverse-biased diode, having reverse-bias-voltage-dependent junction depletion capacitance, said reverse-biased diode thus serving the function of said capacitor element;

wherein said reverse-biased diode is a PN diode with contact to the P-layer which includes windows into said contact and into said P-layer down to said adjoining N-layer, and said diode element is a GaAs P⁺ PiN diode, said reverse-biased diode and said diode element being integrally formed in a single crystal.

3. A current-controlled capacitor system, comprising:

(a) a capacitor element; and

(b) a diode element in series with said capacitor element, said diode element being a forward-biased GaAs PiN diode having a carrier concentration in the i-region of less than about 10¹² cm^-3, the system being further characterized in that;

(o) said forward-biased diode element conducts a forward current which acts to control the forward-bias diffusion capacitance of said diode element;

(i) said diode element has a capacitance which is less than the capacitance of said capacitor element when said diode element is under zero bias;

(ii) said diffusion capacitance of said diode element is controlled by varying said forward current through said diode element;

(iii) said forward current acting to control said diffusion capacitance of said diode element is selected such that the total capacitance, Cmin, of the current-controlled capacitor system is 1.1 times the zero-bias depletion capacitance, C_t (0), of said diode element at some minimum value of forward current, I_min ; and

,

(iv) the total capacitance, Cmax, of the current-controlled capacitor system is 0.9 times the capacitance, C₁, of said capacitor element at some greater value of forward current, I_max ;

wherein said capacitor element is a reverse-biased diode, having reverse-bias-voltage-dependent junction depletion capacitance, said reverse-biased diode thus serving the function of said capacitor element;

wherein said diode element is a GaAs PiN structure grown on a N⁺ substrate and having an ohmic contact to the N-layer, said reverse-biased diode being the N⁺ P junction, where said N⁺ portion of said N⁺ P junction is said N⁺ substrate, with said reverse-biased diode and said diode element being integrally formed in a single crystal.

4. A current-controlled capacitor system, comprising:

(a) a capacitor element; and

(b) a diode element in series with said capacitor element, said diode element being a forward-biased GaAs PiN diode having a carrier concentration in the i-region of less than about 10¹² cm^-3, the system being further characterized in that;

(o) said forward-biased diode element conducts a forward current which acts to control the forward-bias diffusion capacitance of said diode element;

(i) said diode element has a capacitance which is less than the capacitance of said capacitor element when said diode element is under zero bias;

(ii) said diffusion capacitance of said diode element is controlled by varying said forward current through said diode element;

(iii) said forward current acting to control said diffusion capacitance of said diode element is selected such that the total capacitance, Cmin, of the current-controlled capacitor system is 1.1 times the zero-bias depletion capacitance, C_t (0), of said diode element at some minimum value of forward current, I_min ; and

,

(iv) the total capacitance, Cmax, of the current-controlled capacitor system is 0.9 times the capacitance, C₁, of said capacitor element at some greater value of forward current, I_max ;

wherein said capacitor element is a reverse-biased diode, having reverse-bias-voltage-dependent junction depletion capacitance, said reverse-biased diode thus serving the function of said capacitor element;

wherein said diode element is a GaAs PiN structure grown on an N⁺ substrate and having a Schottky barrier with the N-layer, said reverse-biased diode being the N⁺ P junction and Schottky barrier, with said reverse-biased diode and said diode element being integrally formed in a single crystal.

13. A system as in claim 4 wherein said Schottky barrier of said reverse-biased diode is transparent.

5. A current-controlled capacitor system, comprising:

(a) a capacitor element; and

(b) a diode element in series with said capacitor element, said diode element being a forward-biased GaAs PiN diode having a carrier concentration in the i-region of less than about 10¹² cm^-3, the system being further characterized in that;

(o) said forward-biased diode element conducts a forward current which acts to control the forward-bias diffusion capacitance of said diode element;

(i) said diode element has a capacitance which is less than the capacitance of said capacitor element when said diode element is under zero bias;

(ii) said diffusion capacitance of said diode element is controlled by varying said forward current through said diode element;

(iii) said forward current acting to control said diffusion capacitance of said diode element is selected such that the total capacitance, Cmin, of the current-controlled capacitor system is 1.1 times the zero-bias depletion capacitance, C_t (0), of said diode element at some minimum value of forward current, I_min ; and

,

(iv) the total capacitance, Cmax, of the current-controlled capacitor system is 0.9 times the capacitance, C₁, of said capacitor element at some greater value of forward current, I_max ;

wherein said capacitor element is a reverse-biased diode, having reverse-bias-voltage-dependent junction depletion capacitance, said reverse-biased diode thus serving the function of the capacitor element;

wherein a plurality of systems

wherein said reverse-biased diode is a GaAs Schottky diode with contact to the N-layer which includes windows in said Schottky contact and said diode element is a GaAs P⁺ PiN diode, said reverse-biased diode and said diode element being integrally formed in a single crystal

are grown on a single P⁺ substrate so as to be separated from each other by etching down to the P-layer, so as to form an integrated matrix of controlled capacitors.

6. A current-controlled capacitor system, comprising:

(a) a capacitor element; and

(b) a diode element in series with said capacitor element, said diode element being a forward-biased GaAs PiN diode having a carrier concentration in the i-region of less than about 10¹² cm^-3, the system being further characterized in that;

(o) said forward-biased diode element conducts a forward current which acts to control the forward-bias diffusion capacitance of said diode element;

(i) said diode element has a capacitance which is less than the capacitance of said capacitor element when said diode element is under zero bias;

(ii) said diffusion capacitance of said diode element is controlled by varying said forward current through said diode element;

(iii) said forward current acting to control said diffusion capacitance of said diode element is selected such that the total capacitance, Cmin, of the current-controlled capacitor system is 1.1 times the zero-bias depletion capacitance, C_t (0), of said diode element at some minimum value of forward current, I_min ; and

,

(iv) the total capacitance, Cmax, of the current-controlled capacitor system is 0.9 times the capacitance, C₁, of said capacitor element at some greater value of forward current, I_max ;

wherein said capacitor element is a reverse-biased diode, having reverse-bias-voltage-dependent junction depletion capacitance, said reverse-biased diode thus serving the function of said capacitor element;

wherein said reverse-biased diode is a PN diode with contact to the P-layer which includes windows into said contact and into said P-layer down to said adjoining N-layer, and said diode element is a GaAs P⁺ PiN diode, said reverse-biased diode and said diode element being integrally formed in a single crystal

are grown on a single P⁺ substrate so as to be separated from each other by etching down to the P-layer of said P⁺ PiN diode, so as to form an integrated matrix of controlled capacitors.

7. A current-controlled capacitor system, comprising:

a capacitor element; and

(b) a diode element in series with said capacitor element, said diode element being a forward-biased GaAs Schottky diode, the system being further characterized in that;

(o) said forward-biased diode element conducts a forward current which acts to control the forward-bias diffusion capacitance of said diode element;

(i) said diode element has a capacitance which is less than the capacitance of said capacitor element when said diode element is under zero bias;

(ii) said diffusion capacitance of said diode element is controlled by varying said forward current through said diode element;

(iii) said forward current acting to control said diffusion capacitance of said diode element is selected such that the total capacitance, Cmin, of the current-controlled capacitor system is 1.1 times the zero-bias depletion capacitance, C_t (0), of said diode element at some minimum value of forward current, I_min ; and

,

(iv) the total capacitance, Cmax, of the current-controlled capacitor system is 0.9 times the capacitance, C₁, of said capacitor element at some greater value of forward current, I_max ;

wherein said capacitor element is a reverse-biased diode, having reverse-bias-voltage-dependent junction depletion capacitance, said reverse-biased diode thus serving the function of said capacitor element;

wherein said reverse-biased diode is a GaAs P⁺ PiN diode, said reverse-biased diode being fabricated by growing a GaAs PiN structure on a P⁺ substrate, and wherein said diode element is a Schottky barrier to the N-layer, the cross sectional area of said Schottky barrier being smaller than that of the P⁺ PiN diode GaAs.

8. A system as in claim 7 wherein said reverse-biased diode is a GaAs P⁺ PiN diode with an ohmic contact to the N-layer which includes windows in said ohmic contact and in said N-layer down to the i-layer.

9. A current-controlled capacitor system, comprising:

(a) a capacitor element; and

(b) a diode element in series with said capacitor element, said diode element being a forward-biased GaAs Schottky diode, the system being further characterized in that;

(o) said forward-biased diode element conducts a forward current which acts to control the forward-bias diffusion capacitance of said diode element;

(i) said diode element has a capacitance which is less than the capacitance of said capacitor element when said diode element is under zero bias;

(ii) said diffusion capacitance of said diode element is controlled by varying said forward current through said diode element;

(iii) said forward current acting to control said diffusion capacitance of said diode element is selected such that the total capacitance, Cmin, of the current-controlled capacitor system is 1.1 times the zero-bias depletion capacitance, C_t (0), of said diode element at some minimum value of forward current, I_min ; and

,

(iv) the total capacitance, Cmax, of the current-controlled capacitor system is 0.9 times the capacitance, C₁, of said capacitor element at some greater value of forward current, I_max ;

wherein said capacitor element is a reverse-biased diode, having reverse-bias-voltage-dependent junction depletion capacitance, said reverse-biased diode thus serving the function of said capacitor element;

wherein said reverse-biased diode is a GaAs P⁺ PiN diode, said reverse-biased diode being fabricated by growing a GaAs PiN structure on a P⁺ substrate, and wherein said diode element is a Schottky barrier to the N-layer, the cross sectional area of said Schottky barrier being smaller than that of the P⁺ PiN diode, wherein a plurality of structures

are grown on a single P⁺ substrate and are separated from each other by etching down to the i-layer of the P⁺ PiN structure.

10. A system as in claim 9 wherein said reverse-biased diode GaAs P⁺ PiN diode has an ohmic contact to the N-layer which includes windows in said ohmic contact and in said N-layer down to the i-layer.

11. A current-controlled capacitor system, comprising:

(a) a capacitor element; and

(b) a diode element in series with said capacitor element, said diode element being a forward-biased GaAs PiN diode having a carrier concentration in the i-region of less than about 10¹² cm^-3, the system being further characterized in that;

(o) said forward-biased diode element conducts a forward current which acts to control the forward-bias diffusion capacitance of said diode element;

(i) said diode element has a capacitance which is less than the capacitance of said capacitor element when said diode element is under zero bias;

(ii) said diffusion capacitance of said diode element is controlled by varying said forward current through said diode element;

(iii) said forward current acting to control said diffusion capacitance of said diode element is selected such that the total capacitance, Cmin, of the current-controlled capacitor system is 1.1 times the zero-bias depletion capacitance, C_t (0), of said diode element at some minimum value of forward current, I_min ; and

,

(iv) the total capacitance, Cmax, of the current-controlled capacitor system is 0.9 times the capacitance, C₁, of said capacitor element at some greater value of forward current, I_max ;

wherein said GaAs PiN diode element structure grown on a first surface of a GaAs substrate having first and second surfaces, and said capacitor element is a reverse-biased PiN diode, said reverse-biased PiN diode being formed on said second surface of said GaAs substrate, with said reverse-biased PiN diode and said diode element thereby being integrally formed in a single said GaAs substrate, on opposite surfaces of said single GaAs substrate.

12. A system as in claim 11 wherein said reverse-biased diode is a GaAs P⁺ PiN diode with an ohmic contact to the N-layer which includes windows in said ohmic contact and in said N-layer down to the i-layer.