A Study Of The Effect Of Proton Irradiation On The Electrical Characteristics Of InP/inGaAs HBTs

More and more attention is paid to Heterojunction Bipolar Transistors(HBTs) due to their unique advantages. HBTs based on In P/In Ga As compared with other HBTs are of particular interest since many of their features are attractive for high speed and high frequency applications. These include higher electron mobility in the In Ga As base, higher velocity overshoot in the collector, higher thermal conductivity of substrate and lower surface recombination velocity. The reliability of these devices in radiation environment is an important issue particularly in space-based communication systems. Proton is one of the domain particles in space and proton irradiation has an effect on the In P/In Ga As HBTs. So it is necessary to investigate the proton irradiation performance of In P/In Ga As HBTs.The proton-induced degradation in In P/In Ga As heterojunction bipolar transistors(HBTs) is studied in this thesis. The experiments of 3Me V and 10 Me V proton radiation on In P/In Ga As HBTs and In P/In Ga As heterojunction structure have been performed. The proton beam was 0.027 n A/cm2?s and the proton fluences were 1×1011, 5×1011, 1×1012 and 5×1012 protons/cm2. Based on the physics of heterojunction bipolar transistors and concepts of radiation damage mechanisms, the radiation effects were analyzed.After the proton irradiation, Current-Voltage(I-V) measurements and Capacitance-Voltage(C-V) measurements were performed. The noticeable change in I-V characteristics was the increase in the forward and inverse current with the increase in proton fluence. A bigger increase in capacitance was caused by the fluences of 1×1012p/cm2 than 5×1011p/cm2. Also, a bigger increase in capacitance was caused by the proton irradiation with 3Me V energy than 10 Me V energy. The interface states density was calculated based on the frequency dependent C-V measurements. The result showed that the interface state density increased with the increase in the proton fluence and more interface states were induced by the lower energy irradiation.After the proton irradiation, output characteristics(IC-VCE) measurements and Gummel measurements were performed. The result showed a degradation in gain. The gain degradation after different proton fluences indicated that the higher-fluence proton caused more severe damage. However, the lower-energy protons caused much more damage because of its more energy deposition in the active device region. The increase in base current due to the increased recombination was responsible for the noticeable current gain degradation.The proton-induced degradation for In P/In Ga As heterojunction bipolar transistors(HBTs) was studied based on the calculation in the energy range from the displacement damage threshold to 100 Me V with analytical model of nonionizing energy loss(NIEL). Qualitative comparison of the NIEL results with the proton damage coefficients for In P/In Ga As HBTs was made and good correlation was found. The SRIM simulation results showed that the vacancy density increased with the increase in proton fluences.