ABSTRACT
A b stra c t........................................................................................... 48 1. In tro d u c tio n ................................................................................... 48 2. Material Parameters of GaN-based Semiconductors Important
for Their Applications in FETs and Photodetectors.................... 49 3. Epitaxial Growth, Processing, Ohmic and Schottky Contacts
and AlGaN/GaN/InN Band L in e u p s ............................................ 52 4. GaN-based Field Effect T ra n s is to rs ............................................ 55
4.1. Designs of GaN-based Field Effect Transistors ................ 55 4.2. High Temperature Performance and AlGaN/GaN Doped
Channel H FE T s....................................... 58 4.3. Doped Channel H F E T ............................................................ 60 4.4. Role of Piezoelectric E ffec t.................................................... 62 4.5. Maximum Currents and Breakdown Voltages of GaN-based
HFETs ................................................................................... 65 4.6. Self-heating and GaN/AlGaN HFETs on SiC Substrates . . 65 4.7. GaN-based Heterojunction Bipolar Transistors.................... 67
5. GaN-based Photodetectors............................................................ 67 5.1. GaN and AlGaN Photodetector T y p e s ................................ 67 5.2. Photodetector Characteristics................................................ 69 R esponsivity ................................................................................... 69 Photoconductive G a i n .................................................................... 70
Detectivity and Noise Equivalent Power ( N E P ) ................ 72 N o i s e ....................................................................................... 73
5.3. Photoconductive GaN and AlGaN Photodetectors . . . . 74 5.4. Schottky Barrier and p — n Junction GaN Photodetectors . 76 5.5. GaN Metal-Semiconductor-Metal Photodetectors . . . . 81 5.6. Avalanche Breakdown and Breakdown Luminescence
in p-7r-n GaN D i o d e s ............................................................ 82 5.7. Gated Photodetector Based on GaN/AlGaN Heterostructure
Field Effect T ransisto r............................................................ 82 5.8. Emissive UV P hotodetecto rs................................................ 83
6. Challenges and Future Improvements in GaN Photodetector and FET Technology .................................................................... 85 Acknowledgm ent........................................................................... 85 R eferences....................................................................................... 86
Recent improvements in material quality and contact technology for GaNbased materials system have led to a rapid progress in GaN devices. These devices include blue-green lasers [1], blue and green Light Emitting Diodes [2], Ultraviolet (UV) photodetectors [3,4] GaN Avalanche Photo Diodes [5], and AlGaN/GaN Heterostructure Field Effect Transistors [6-11].
