AlGaAs/GaAs HBT 의 열적 안정성 및 고주파 특성 보장을 위한 Emitter Ledge 설계에 관한 연구
- AlGaAs/GaAs HBT 의 열적 안정성 및 고주파 특성 보장을 위한 Emitter Ledge 설계에 관한 연구
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- This dissertation investigates a design of the minimum length of the emitter ledge that achieves the thermal stability and ensures RF characteristics of the AlGaAs/GaAs heterojunction bipolar transistors (HBTs). The HBTs use a p+-base layer to implement base ballast resistors, a fully-depleted AlGaAs ledge to implement input bypass capacitors, and boron ion implantation to reduce the base-collector parasitic capacitance. The dependency of RF characteristics on electrical parameters and geometric parameters is progressed and the method for securing the thermal stability with minimal degradation of the RF characteristics is proposed.
The minimum emitter ledge length for the experimental HBTs is estimated theoretically as 8.27μm, at which power density is 2.77 mW/μm2. The experimental HBT with emitter ledge length of 10 μm has 2 % lower fmax and 4.3 % lower froll-off than the HBTs without the emitter ledge. Experimental results show that the HBTs were thermally stable at an emitter ledge length of 10 μm, and their RF properties were degraded little from those of the HBTs without the emitter ledge when the n- collector underneath the emitter ledge was implanted with boron ions.
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