Room-Temperature p-n-p AlGaAsSb–InGaAsSb Heterojunction Phototransistors With Cutoff Wavelength at 2.5 m

Novel p-n-p AlGaAsSb-InGaAsSb heterojunction phototransistors (HPTs) grown by solid-source molecular beam epitaxy have been proposed and demonstrated. The p-n-p phototransistor structure provides a higher emitter injection ratio than its n-p-n counterpart, due to the large conduction band offset and almost continuous valence band edges between InGaAsSb and AlGaAsSb quaternary alloys. The resulting HPT devices exhibit high responsivities under a bias voltage above 0.3 V. A high room-temperature spectral responsivity of 2984 A/W is achieved at 2.24 mum, corresponding to an optical gain of 1652. The 50% cutoff wavelength of spectral photoresponse at room temperature is 2.50 mum. A room-temperature specific detectivity (D^*) of 8.3times10 ¹¹ cm middot Hz^1/2/W is obtained