COMPARISON OF PARTIALLY RELAXED INGAAS GAAS BASED HIGH-PERFORMANCE PHOTOTRANSISTORS/

We report on heterojunction phototransistors (HPTs) operating at GaAs substrate transparent wavelengths beyond 900 nm, utilizing a strained InGaAs quantum well based absorbing region. High performances have bee n measured with responsivities of approximate to 80 and 200 A/W at 10 and 50 mu W, respectively. The results correspond to electrical curren t gains of up to 3000 for currents of approximate to 10 mA, the best r eported results for such phototransistor structures. The effect of str ain relaxation on device performance is examined, and it is seen that it can cause a degradation both in terms of the transistor and photodi ode characteristics of the HPT. (C) 1996 American Institute of Physics .