Experimental Investigation of Low Frequency Noise Properties of AlGaAs/GaAs and GaInP/GaAs Heterojunction Bipolar Transistors

摘要

The intrinsic low frequency noise characteristics of AlGaAs/GaAs and GalnP/GaAs HBTs have been studied. HBTs with large emitter size of 120 × 120μm~2 have been fabricated on MOCVD-grown abrupt junction emitter materials without undoped spacer layer. The leakage current of GalnP/GaAs HBTs is a little lower than that of AlGaAs/GaAs HBTs. However, AlGaAs/ GaAs HBTs have 10 ～ 25 dB lower noise level than GalnP/GaAs HBTs. For GalnP/GaAs HBTs, the base current noise power spectral densities are proportional to ～exp(V_(BE)/V_T) at a low current level(Ic ≤ 1mA) and saturate at a high current level. This is due to the gain-creeping effect of HBT originating from the persistent band discontinuity. Thus, the dominant noise generation process occurs at the base side of hetero-interface, which is very noisy. But AlGaAs/GaAs HBT noise source is the recombination at the base region.