Abstract

The hetcrojunction phototransistor (HPT), with its inherent gain, is an attractive component for future optical interconnection systems [1]. The use of InGaAs as the absorbing medium is driven by the desire to operate at GaAs substrate transparent wavelengths. However, a trade-off exists between an increase in the thickness of absorbing material, and the onset of lattice relaxation giving rise to defects which degrade the devices. In this work we compare three HPTs, using 12, 20 and 30 strained InGaAs quantum wells (QWs), respectively, as the absorber. We show that all have high performance, but that lattice relaxation does cause a degradation in the device characteristics. The HPTs are of an n-p-i-n configuration grown on n-type GaAs substrate, similar to those previously reported [2]. The 1µm intrinsic collector region consists of GaAs within which are buried the different sets of InGaAs QWs.

© 1996 IEEE