High electron mobility transistor

• US 6,242,766 B1
• Filed: 11/18/1999
• Issued: 06/05/2001
• Est. Priority Date: 03/19/1999
• Status: Expired due to Fees

• Current Assignee: Fujitsu Quantum Devices Limited (Fujitsu Limited)
• Original Assignee: Fujitsu Quantum Devices Limited (Fujitsu Limited)
• Inventors: Tateno, Yasunori
• Primary Examiner(s): Thomas, Tom
• Assistant Examiner(s): Kang, Donghee
• Application Number:
  US09/443,210
• Time in Patent Office: 565 Days
• Field of Search: 257/194, 257/192, 257/20, 257/24, 257/195
• US Class Current: 257/194
• CPC Class Codes: H01L 29/155 Comprising only semiconductor materials H01L29/154 takes precedence
• CPC Class Codes: H01L 29/7783 using III-V semiconductor material

Abstract

A high electron mobility transistor including an n-type semiconductor layer having a mixed crystal of aluminum gallium arsenide with an aluminum mixed ratio set to fall in the range of 0.2˜0.3, and an undoped semiconductor layer forming a superlattice structure of an electron supplying layer, the undoped semiconductor layer having a mixed crystal of aluminum gallium arsenide with an aluminum mixed ratio set to fall in the proximity of a critical mixed crystal ratio between direct transition and indirect transition.

Claims

1. A high electron mobility transistor comprising:

a substrate;

a channel layer formed on said substrate;

an electron-supplying layer formed on said substrate; and

a two-dimensional electron gas formed in said channel layer;

said electron-supplying layer having a superlattice structure and comprising an alternating repetition of;

an n-type semiconductor layer of a mixed crystal of aluminum gallium arsenide having a composition represented as Al_xGa_1-xAs, with an aluminum content x set to fall in the range between 0.2 and about 0.3; and

an undoped semiconductor layer of a mixed crystal of aluminum gallium arsenide having a composition represented as Al_yGa_1-yAs, with an aluminum content y set to fall in the vicinity of a critical Al-content at which a transition occurs in an AlGaAs mixed crystal from a direct transition type to an indirect transition type.

2. The high electron mobility transistor as claimed in claim 1, wherein undoped semiconductor layer has a conduction band energy level for the Γ

-valley lower than the energy level for any of the X-valley and the L-valley.

3. The high electron mobility transistor as claimed in claim 2, wherein said aluminum content y of said undoped semiconductor layer has a value between about 0.4 and about 0.5.

4. A high electron mobility transistor comprising:

a substrate;

a channel layer formed of a mixed crystal of InGaAs having a composition represented as In_zGa_1-zAs, with an In-content z set in the range between about 0.1 and about 0.3, being formed on said substrate;

an electron-supplying layer formed on said substrate; and

a two-dimensional electron gas formed in said channel layer;

said electron-supplying layer having a superlattice structure comprising an alternating repetition of;

an n-type semiconductor layer of a mixed crystal of aluminum gallium arsenide having a composition represented as Al_xGa_1-xAs, with an aluminum mixed content x set smaller than about 0.3; and

an undoped semiconductor spacer layer of a mixed crystal of aluminum gallium arsenide having a composition represented as Al_yGa_1-yAs, with an aluminum content y set to fall in the range between about 0.4 and about 0.5.