DC and high-frequency performance of AlGaN/GaN Heterojunction Bipolar Transistors
نویسندگان
چکیده
The DC and high frequency performance of AlGaN/GaN Heterojunction Bipolar Transistors (HBTs) is analyzed using an enhanced drift-diusion model and GaN/AlGaN material parameters, which were previously veri®ed by modeling experimental device characteristics. The emitter±base diode turn-on voltage is as high as 2.7 V while the collector and base ideality factors are 1.16 and 1.46 respectively. A DC current gain of b=15 is found at a collector current density of 2.5 kA/cm and the gain is maintained at this value up to 4.1 kA/cm. The devices show a small oset voltage of 0.5 V. A forward breakdown voltage BVCEO of 70 V is found for designs with collector doping of 5 10 cmÿ3. The current gain varied from 22 to 6 when the base doping was increased from 5 10 to 2 10 cmÿ3. At the same time, the maximum oscillation frequency fMAX increased from 3 to 6 GHz. A severe degradation of the current gain, fT, and fMAX was observed for HBT designs with a base thickness wider than 1000 AÊ . By optimizing the transistor design and bias, an fT of 44 GHz and an fMAX of 24 GHz are predicted. Results of a large-signal analysis are also presented to evaluate the power capability and eciency of AlGaN/GaN HBTs. # 2000 Elsevier Science Ltd. All rights reserved.
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