Efficient carrier injection in a semiconductor device

• US 7,829,912 B2
• Filed: 04/16/2007
• Issued: 11/09/2010
• Est. Priority Date: 07/31/2006
• Status: Active Grant

• Current Assignee: II-VI Delaware, Inc. (Coherent Corp.)
• Original Assignee: Finisar Corporation (II-VI Incorporated)
• Inventors: Johnson, Ralph H.
• Primary Examiner(s): Monbleau; Davienne
• Assistant Examiner(s): Rodela; Eduardo A
• Application Number:
  US11/735,993
• Publication Number:
  US 20080023688A1
• Time in Patent Office: 1,303 Days
• Field of Search: 372/43.01, 372/44.01, 372/45.011, 372/45.012, 372/45.013, 372/45.01, 257/79, 257/101, 257/E33.011
• US Class Current: 257/101
• CPC Class Codes: H01L 29/201 including two or more compounds , e.g. alloys H01L29/2006 takes precedence
• CPC Class Codes: H01L 33/06 within the light emitting region, e.g. quantum confinement structure or tunnel barrier
• CPC Class Codes: H01L 33/30 containing only elements of Group III and Group V of the Periodic Table
• CPC Class Codes: H01S 5/0421 characterised by the semiconducting contacting layers electrodes H01S5/0425
• CPC Class Codes: H01S 5/18308 having a special structure for lateral current or light confinement
• CPC Class Codes: H01S 5/3211 characterised by special cladding layers, e.g. details on band-discontinuities

Abstract

Semiconductor devices such as VCSELs, SELs, LEDs, and HBTs are manufactured to have a wide bandgap material near a narrow bandgap material. Electron injection is improved by an intermediate structure positioned between the wide bandgap material and the narrow bandgap material. The intermediate structure is an inflection, such as a plateau, in the ramping of the composition between the wide bandgap material and the narrow bandgap material. The intermediate structure is highly doped and has a composition with a desired low electron affinity. The injection structure can be used on the p-side of a device with a p-doped intermediate structure at high hole affinity.

Claims

1. A semiconductor device with efficient carrier injection from a wide bandgap semiconductor material into a narrower bandgap semiconductor material, the semiconductor device comprising:

a first semiconductor material having a desired bandgap;

an injection structure adjacent the first semiconductor material, the injection structure comprising;

a confining region formed from a second semiconductor material having a wider bandgap than the first semiconductor material; and

a transition region positioned between the first and second semiconductor materials, the transition region comprising a first ramp portion in which a composition is gradually ramped and a doped intermediate structure, the doped intermediate structure having an inflection in the ramping of the composition wherein (i) the intermediate structure is n-doped and the electron affinity at the inflection is lower than the electron affinity of the confining region or (ii) the intermediate structure is p-doped and the hole affinity at the inflection is higher than the hole affinity of the confining region, wherein the ramping of the composition comprises a change in the content of Al, P, or Si and the change in content of the Al, P, or Si provides an electron affinity minimum or a hole affinity maximum within the ramping and the inflection occurs at an Al, P, or Si content that is within 20% of the electron affinity minimum or the hole affinity maximum.

2. A semiconductor device as in claim 1, wherein the intermediate structure comprises a plateau in the ramping of the composition.

3. A semiconductor device as in claim 1, wherein the injection structure comprises a material selected from the group consisting of AlGaAs, AlGaInP, GaAsP, or SiGe.

4. A semiconductor device as in claim 1, wherein the inflection occurs at an aluminum content that is within 10% of the electron affinity minimum or the hole affinity maximum.

5. A semiconductor device as in claim 1, wherein the thickness of the confining region is in a range from about 5 nm to about 100 nm.

6. A semiconductor device as in claim 1, wherein the intermediate structure has a thickness in a range from about 5 nm to 100 nm.

7. A semiconductor device as in claim 1, wherein the doping in the intermediate structure is greater than about 5×

10¹⁷/cm³.

8. A semiconductor device as in claim 1, wherein the dopant level in the confining region is in a range of about 5×

10¹⁷/cm³ to about 1×

10¹⁹/cm³.

9. A semiconductor device as in claim 1, further comprising a spacer layer adjacent the confining region and having an aluminum content that is less than the aluminum content of the confining region.

10. A semiconductor device as in claim 1, wherein the semiconductor device comprises an active region and the first semiconductor material is deposited in the active region.

11. A semiconductor device as in claim 10, wherein the transition region further comprises a substantially undoped portion that is adjacent the active region.

12. A semiconductor device as in claim 1, wherein the semiconductor device comprises a heterojunction bipolar transistor.

13. A semiconductor device as in claim 1, wherein the intermediate structure is n-doped and the electron affinity at the inflection is lower than the electron affinity of the confining region.

14. A semiconductor device as in claim 1, wherein the intermediate structure is p-doped and the hole affinity at the inflection is higher than the hole affinity of the confining region.

15. A semiconductor device as in claim 1, wherein the ramping of the composition in the ramp portion is substantially continuous and wherein the inflection comprises a discontinuity in the ramping.

16. A semiconductor device as in claim 1, wherein the semiconductor device comprises an active region and the first semiconductor material is a quantum well barrier in the active region.

17. A semiconductor device with efficient carrier injection from a wide bandgap semiconductor material into a narrower bandgap semiconductor material, the semiconductor device comprising:

a first semiconductor material having a desired bandgap;

an injection structure adjacent the first semiconductor material, the injection structure comprising;

a confining region formed from a second semiconductor material having a wider bandgap than the first semiconductor material; and

a transition region positioned between the first and second semiconductor materials, the transition region comprising a first ramp portion in which a composition is gradually ramped and a doped intermediate structure, the doped intermediate structure having an inflection in the ramping of the composition wherein (i) the intermediate structure is n-doped and the electron affinity at the inflection is lower than the electron affinity of the confining region or (ii) the intermediate structure is p-doped and the hole affinity at the inflection is higher than the hole affinity of the confining region, wherein the inflection occurs at an aluminum content that is within 15% of the electron affinity minimum or the hole affinity maximum.

18. A semiconductor device with efficient carrier injection from a wide bandgap semiconductor material into a narrower bandgap semiconductor material, the semiconductor device comprising:

a first semiconductor material having a desired bandgap;

an injection structure adjacent the first semiconductor material, the injection structure comprising;

a confining region formed from a second semiconductor material having a wider bandgap than the first semiconductor material; and

a transition region positioned between the first and second semiconductor materials, the transition region comprising a first ramp portion in which a composition is gradually ramped and a doped intermediate structure, the doped intermediate structure having an inflection in the ramping of the composition wherein (i) the intermediate structure is n-doped and the electron affinity at the inflection is lower than the electron affinity of the confining region or (ii) the intermediate structure is p-doped and the hole affinity at the inflection is higher than the hole affinity of the confining region, wherein the confining region comprises a second ramp portion in which the composition is ramped and wherein the doped intermediate structure having the inflection is between the first and second ramp portions.