Field effect transistor, display element, image display device, and system

• US 9,105,473 B2
• Filed: 02/15/2011
• Issued: 08/11/2015
• Est. Priority Date: 02/16/2010
• Status: Active Grant

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Ueda, Naoyuki, Nakamura, Yuki, Sone, Yuji, Abe, Yukiko
• Primary Examiner(s): Such, Matthew W
• Assistant Examiner(s): Smith, Stephen C
• Application Number:
  US13/578,782
• Publication Number:
  US 20120306834A1
• Time in Patent Office: 1,638 Days
• US Class Current: 1/1
• CPC Class Codes: H01L 21/02565 Oxide semiconducting materials not being Group 12/16 materials, e.g. ternary compounds
• CPC Class Codes: H01L 21/02576 N-type
• CPC Class Codes: H01L 21/02631 Physical deposition at reduced pressure, e.g. MBE, sputtering, evaporation
• CPC Class Codes: H01L 27/1225 with semiconductor materials not belonging to the group IV of the periodic table, e.g. InGaZnO
• CPC Class Codes: H01L 29/7869 having a semiconductor body comprising an oxide semiconductor material, e.g. zinc oxide, copper aluminium oxide, cadmium stannate
• CPC Class Codes: H10K 59/1213 the pixel elements being TFTs

Abstract

A disclosed field effect transistor includes a gate electrode to which a gate voltage is applied, a source electrode and a drain electrode for acquiring a current in response to the gate voltage, an active layer provided adjacent to the source electrode and the drain electrode, the active layer being formed of an n-type oxide semiconductor, and a gate insulator layer provided between the gate electrode and the active layer. In the field effect transistor, the n-type oxide semiconductor is formed of an n-type doped compound having a chemical composition of a crystal phase obtained by introducing at least one of a trivalent cation, a tetravalent cation, a pentavalent cation and a hexavalent cation.

Claims

1. A field effect transistor comprising:

a gate electrode to which a gate voltage is applied;

a source electrode and a drain electrode that acquire a current in response to the gate voltage;

an active layer located adjacent to the source electrode and the drain electrode, the active layer comprising a metal oxide semiconductor of n-type; and

a gate insulator layer located between the gate electrode and the active layer,

wherein the metal oxide semiconductor comprises an n-type substitutional doped oxide with a crystal composition, wherein the n-type doped compound comprises at least one dopant wherein all dopant valences are larger than that of a valence of a metal in the metal oxide semiconductor for which the dopant is being substitutionally doped.

2. The field effect transistor of claim 1,

wherein the n-type substitutional doped oxide with the crystal composition has a composition of a cubic crystal system.

3. The field effect transistor of claim 2,

wherein the cubic crystal system is a spinel compound represented by AB₂O₄ where A is at least one divalent cation selected from the group consisting of Mg²⁺, Zn²⁺, and Cd²⁺, and B is at least one trivalent cation selected from the group consisting of Al³⁺, Ga³⁺, and In³⁺.

4. The field effect transistor of claim 3, wherein the spinel compound is selected from the group consisting of MgGa₂O₄, MgIn₂O₄, ZnAl₂O₄, ZnGa₂O₄, and CdGa₂O₄.

5. The field effect transistor of claim 3,

wherein a part of the cation A of AB₂O₄ of the spinel compound is substituted by at least one cation selected from the group consisting of Al³⁺, Ga³⁺, In³⁺, Ge⁴⁺, Sn⁴⁺, Ti⁴⁺, Zr⁴⁺, Hf⁴⁺, V⁵⁺, Nb⁵⁺, Ta⁵⁺, Sb⁵⁺, Mo⁶⁺, and W⁶⁺.

6. The field effect transistor of claim 3,

wherein a part of the cation B of AB₂O₄ of the spinel compound is substituted by at least one cation selected from the group consisting of Ge⁴⁺, Sn⁴⁺, Ti⁴⁺, Zr⁴⁺, Hf⁴⁺, V⁵⁺, Nb⁵⁺, Ta⁵⁺, Sb⁵⁺, Mo⁶⁺, and W⁶⁺.

7. The field effect transistor of claim 2,

wherein the cubic crystal system is a spinel compound represented by A₂DO₄ where A is at least one divalent cation selected from the group consisting of Mg²⁺, Zn²⁺, and Cd²⁺, and D is at least one tetravalent cation selected from the group consisting of Ti⁴⁺, and Sn⁴⁺.

8. The field effect transistor of claim 7, wherein the spinel compound is selected from the group consisting of Mg₂SnO₄, Zn₂TiO₄, Zn₂SnO₄, and Cd₂SnO₄.

9. The field effect transistor of claim 7,

wherein a part of the cation A of A₂DO₄ of the spinel compound is substituted by at least one cation selected from the group consisting of Al³⁺, Ga³⁺, In³⁺, Ge⁴⁺, Sn⁴⁺, Ti⁴⁺, Zr⁴⁺, Hf⁴⁺, V⁵⁺, Nb⁵⁺, Ta⁵⁺, Sb⁵⁺, Mo⁶⁺, and W⁶⁺.

10. The field effect transistor of claim 7,

wherein a part of the cation D of A₂DO₄ of the spinel compound is substituted by at least one cation selected from the group consisting of V⁵⁺, Nb⁵⁺, Ta⁵⁺, Sb⁵⁺, Mo⁶⁺, and W⁶⁺.

11. The field effect transistor of claim 2,

wherein the cubic crystal system is a bixbite compound comprising at least one trivalent cation selected from the group consisting of In³⁺, SC³⁺, Y³⁺, and Ln³⁺, where Ln is a rare earth element.

12. The field effect transistor of claim 11, wherein the bixbite compound is selected from the group consisting of In₂O₃, Y₂O₃, and La₂O₃.

13. The field effect transistor of claim 11,

wherein a part of the trivalent cation of the bixbite compound is substituted by at least one cation selected from the group consisting of Ge⁴⁺, Sn⁴⁺, Ti⁴⁺, Zr⁴⁺, Hf⁴⁺, V⁵⁺, Nb⁵⁺, Ta⁵⁺, Sb⁵⁺, Mo⁶⁺, and W⁶⁺.

14. The field effect transistor of claim 1,

wherein the crystal composition has a composition of an orthorhombic crystal system.

15. The field effect transistor of claim 14,

wherein the orthorhombic crystal system is an olivine compound represented by A₂GO₄ where A is at least one divalent cation selected from the group consisting of Mg²⁺, Zn²⁺, and Cd²⁺, and G is at least one tetravalent cation selected from the group consisting of Si⁴⁺, Ge⁴⁺, and Sn⁴⁺.

16. The field effect transistor of claim 15,

wherein a part of the cation A of A₂GO₄ of the olivine compound is substituted by at least one cation selected from the group consisting of Al³⁺, Ga³⁺, In³⁺, Ge⁴⁺, Sn⁴⁺, Ti⁴⁺, Zr⁴⁺, Hf⁴⁺, V⁵⁺, Nb⁵⁺, Ta⁵⁺, Sb⁵⁺, Mo⁶⁺, and W⁶⁺.

17. The field effect transistor of claim 15,

wherein a part of the cation G of A₂GO₄ of the olivine compound is substituted by at least one cation selected from the group consisting of V⁵⁺, Nb⁵⁺, Ta⁵⁺, Sb⁵⁺, Mo⁶⁺, and W⁶⁺.

18. The field effect transistor of claim 15, wherein the olivine compound is selected from Cd₂GeO₄, Mg₂GeO₄.

19. The field effect transistor of claim 1,

wherein the crystal composition has a composition of a hexagonal crystal system.

20. The field effect transistor of claim 19,

wherein the hexagonal crystal system is a homologous compound represented by In₂O₃(ZnO)_m where m is an integer of two to six.

21. The field effect transistor of claim 20,

wherein a part of the cation of the homologous compound is substituted by at least one cation selected from the group consisting of V⁵⁺, Nb⁵⁺, Ta⁵⁺, Sb⁵⁺, Mo⁶⁺, and W⁶⁺.

22. The field effect transistor of claim 20, wherein the homologous compound is selected from In₂Zn₂O₅.

23. The field effect transistor of claim 19,

wherein the hexagonal crystal system is a PbSb₂O₆ type compound represented by RE₂O₆ where R is at least one divalent cation selected from the group consisting of Ca²⁺, Sr²⁺, Ba²⁺, Cd²⁺, and Pb²⁺, and E is at least one pentavalent cation selected from the group consisting of Sb⁵⁺, Nb⁵⁺, and Ta⁵⁺.

24. The field effect transistor of claim 23,

wherein a part of the cation R of RE₂O₆ of the PbSb₂O₆ type compound is substituted by at least one cation selected from the group consisting of Al³⁺, Ga³⁺, In³⁺, Ge⁴⁺, Sn⁴⁺, Ti⁴⁺, Zr⁴⁺, Hf⁴⁺, V⁵⁺, Nb⁵⁺, Ta⁵⁺, Sb⁵⁺, Mo⁶⁺, and W⁶⁺.

25. The field effect transistor of claim 23,

wherein a part of the cation E of RE₂O₆ of the PbSb₂O₆ type compound is substituted by at least one cation selected from the group consisting of Mo⁶⁺, and W⁶⁺.

26. The field effect transistor of claim 23, wherein the PbSb₂O₆ type compound is selected from PbSb₂O₆, CdSb₂O₆.

27. A display element comprising:

an optical control element configured to control an optical output based on a driving signal;

the field effect transistor of claim 1; and

a drive circuit configured to drive the optical control element.

28. The display element of claim 27,

wherein the optical control element comprises an element selected from the group consisting of an organic electroluminescent element, an electrochromic element, a liquid crystal element, and an electrophoretic element.

29. An image display device comprising:

a plurality of the display elements of claim 27 arranged in a matrix;

a plurality of wires configured to individually apply gate voltages to a plurality of field effect transistors in the display elements arranged in the matrix; and

a display control device configured to separately control gate voltages of the field effect transistors via the wires based on image data.

30. A system comprising:

the image display device of claim 29; and

an image data generating device configured to generate the image data based on image information to be displayed and output the generated image data to the image display device.

31. The field effect transistor of claim 2,

wherein the n-type substitutional doped oxide with the composition of the cubic crystal system is a pyrochlore compound represented by J₂E₂O₇ where J is at least one divalent cation selected from the group consisting of Ca²⁺, Zn²⁺, and Cd²⁺, and E is at least one pentavalent cation including Sb⁵⁺, Nb⁵⁺, and Ta⁵⁺.

32. The field effect transistor of claim 31,

wherein a part of the cation J of J₂E₂O₇ of the pyrochlore compound is substituted by at least one cation selected from the group consisting of Al³⁺, Ga³⁺, In³⁺, Ge⁴⁺, Sn⁴⁺, Ti⁴⁺, Zr⁴⁺, Hf⁴⁺, V⁵⁺, Nb⁵⁺, Ta⁵⁺, Sb⁵⁺, Mo⁶⁺, and W⁶⁺.

33. The field effect transistor of claim 31,

wherein a part of the cation E of J₂E₂O₇ of the pyrochlore compound is substituted by at least one cation selected from the group consisting of Mo⁶⁺, and W⁶⁺.

34. The field effect transistor of claim 31, wherein the pyrochlore compound is selected from Cd₂Sb₂O₇.

36. The field effect transistor of claim 34, wherein the trirutile compound is selected from the group consisting of ZnSb₂O₆, MgSb₂O₆, and MgTa₂O₆.

35. A field effect transistor, comprising:

a gate electrode to which a gate voltage is applied;

a source electrode and a drain electrode that acquire a current in response to the gate voltage;

an active layer located adjacent to the source electrode and the drain electrode, the active layer comprising a metal oxide semiconductor of n-type; and

a gate insulator layer located between the gate electrode and the active layer,

wherein the metal oxide semiconductor comprises an n-type substitutional doped oxide with a composition of a tetragonal crystal system, wherein the n-type doped compound comprises at least one dopant selected from the group consisting of a trivalent cation, a tetravalent cation, a pentavalent cation and a hexavalent cation,

wherein the tetragonal crystal system is a trirutile compound represented by AE₂O₆ where A is at least one divalent cation selected from the group consisting of Mg²⁺, Zn²⁺, and Cd²⁺, and E is at least one pentavalent cation selected from the group consisting of Sb⁵⁺, Nb⁵⁺, and Ta⁵⁺, and

wherein the n-type doped compound comprises at least one cation selected from the group consisting of Al³⁺, Ga³⁺, In³⁺, Y³⁺, Ge⁴⁺, Sn⁴⁺, Ti⁴⁺, Zr⁴⁺, Hf⁴⁺, V⁵⁺, Nb⁵⁺, Ta⁵⁺, Sb⁵⁺, Mo⁶⁺, and W⁶⁺, and

wherein the valence of the dopant is larger than that of a valence of a metal in the metal oxide semiconductor for which it is being substitutionally doped.

37. The field effect transistor of claim 35,

wherein a part of the cation A of AE₂O₆ of the trirutile compound is substituted by at least one cation selected from the group consisting of Al³⁺, Ga³⁺, In³⁺, Ge⁴⁺, Sn⁴⁺, Ti⁴⁺, Zr⁴⁺, Hf⁴⁺, V⁵⁺, Nb⁵⁺, Ta⁵⁺, Sb⁵⁺, Mo⁶⁺, and W⁶⁺.

38. The field effect transistor of claim 35,

wherein a part of the cation E of AE₂O₆ of the trirutile compound is substituted by at least one cation selected from the group consisting of Mo⁶⁺, and W⁶⁺.