FIELD EFFECT TRANSISTOR, DISPLAY ELEMENT, IMAGE DISPLAY DEVICE, AND SYSTEM

• US 20120306834A1
• Filed: 02/15/2011
• Published: 12/06/2012
• 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
• Granted Patent: US 9,105,473 B2
• Time in Patent Office: Days
• US Class Current: 345/208
• 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 an n-type oxide semiconductor; and

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

wherein the n-type oxide semiconductor comprises an n-type doped compound having a crystal phase, 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.

2. The field effect transistor of claim 1,

wherein the crystal phase comprises a cubic compound.

3. The field effect transistor of claim 2,

wherein the cubic compound 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⁺, and

wherein the n-type doped compound comprises 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⁺.

4. The field effect transistor of claim 2,

wherein the cubic compound 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⁺, and

wherein the n-type doped compound comprises 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⁺.

5. The field effect transistor of claim 2,

wherein the cubic compound 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, and

wherein the n-type doped compound comprises 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 1,

wherein the crystal phase comprises a tetragonal compound.

7. The field effect transistor of claim 6,

wherein the tetragonal compound 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⁺.

8. The field effect transistor of claim 1,

wherein the crystal phase comprises an orthorhombic compound.

9. The field effect transistor of claim 8,

wherein the orthorhombic compound 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⁺, 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⁺.

10. The field effect transistor of claim 1,

wherein the crystal phase comprises a hexagonal compound.

11. The field effect transistor of claim 10,

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

wherein the n-type doped compound comprises at least one cation selected from the group consisting of V⁵⁺, Nb⁵⁺, Ta⁵⁺, Sb⁵⁺, Mo⁶⁺, and W⁶⁺.

12. 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.

13. The display element of claim 12,

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.

14. An image display device comprising:

a plurality of the display elements of claim 12 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.

15. A system comprising:

the image display device of claim 14; 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.

16. The field effect transistor of claim 10,

wherein the hexagonal compound 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⁺, 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⁺.

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

18. The field effect transistor of claim 4, wherein the spinel compound is selected from the group consisting of Mg₂SnO₄, Zn₂TiO₄, Zn₂SnO₄, and Cd₂SnO₄.

19. The field effect transistor of claim 5, wherein the bixbite compound is selected from the group consisting of In₂O₃, Y₂O₃, and La₂O₃.

20. The field effect transistor of claim 7, wherein the trirutile compound is selected from the group consisting of ZnSb₂O₆, MgSb₂O₆, and MgTa₂O₆.