Study Of γ Radiation Effect On InGaP/GaAs HBTs

Compared to common bipolar transistor, InGaP/GaAs HBT is payed much attentionfor its many unique advantages. Its high corrosion, no deep level of recombinationcenters and strong anti-radiation properties, make it have a wide range of applications inthe aerospace, military, nuclear radiation and other fields.In this dissertation, the Win’s InGaP/GaAs HBTs irradiated with γ rays have beeninvestigated. The radiation effects are obversed and the damage mechanisms areanalyzed. The γ irradiation experiment of InGaP/GaAs HBT for different doses is made,γ irradiation total dose up to10Mrad (Si). After irradiation, the InGaP/GaAs HBT’sbase current rises, which makes the current gain reduce. And the annealed base currentcontinues to rises. The above two changes with the increase of total dose.IrradiatedInGaP/GaAs HBT’s cutoff frequency decreases, also related to the increase of total dose,but cutoff frequency decreased slightly after annealing.Carried out on the above analysis,the base current is directly caused by the decease of emitter minority carrier lifetime,which is caused by the increase of interface state density.The decrease of frequencycharacters iscaused by the reduced electron mobility. Physically, the radiation makes thesemiconductor device generate displacement damage, leading to carrier scatteringprobability increased, so that the electron mobility.According to the result of the irradiation experiment, the model used to describeInGaP/GaAs HBT has been amended.In the DC area, the base current formula is improved. A radiation-related variable isinduced in the non-ideal base current coefficient IBEN. The modified base currentformula can describe the relationship between the excess base current and the total doseof γ radiation.In the AC area, the transmission time function expression is improved. A radiationfactor is induced in the forward transit time TF. The revised model reflects well thecharacteristics of irradiated InGaP/GaAs HBT cutoff frequency changes.