III-V semiconductor photodetectors for infrared applications

This thesis demonstrated the III-V semiconductor infrared photodetectors grown by solid source molecular beam epitaxy utilizing novel materials, device structures and substrate orientations. The photodetectors investigated in this thesis have spectral response ranging from 1.3mum to 12mum. Three photodetector structures were investigated: heterojunction photodiodes, heterojunction phototransistors, and superlattice photodiodes.; Chapter 2 and 3 discuss two infrared heterojunction photodiodes at room temperature. Chapter 2 studies an InGaAsSb photodiode with a high detectivity and a 50% cutoff wavelength at 2.6mum. Chapter 3 describes a non-cryogenic InAsSb photodiode with a 50% cutoff wavelength at 4.3mum.; Chapter 4 and 5 present two infrared heterojunction phototransistors (HPTs). A p-n-p InGaAsSb HPT is investigated in Chapter 4 by taking the advantageous band offsets between AlGaAsSb and InGaAsSb. The HPT exhibits a high optical gain and a 50% cutoff wavelength of 2.5mum at room temperature. In Chapter 5, the first InAs HPT structure is proposed and room temperature operation is demonstrated with an optical gain of 8.4 and a 50% cutoff wavelength of 3.5mum.; In Chapter 6, the first type-II InAs/GaSb superlattice photodiodes grown on (311)B GaSb substrate is presented and compared with the corresponding photodiodes grown on (100) GaSb substrate. At 80K, the (311)B devices exhibit longer cutoff wavelength and detectivity twice as high as their (100) counterparts. At last, a mid-IR type-II superlattice photodiode was demonstrated at 80K with cutoff wavelength at 6.6mum. The device exhibits a near BLIP detectivity at 80K and higher temperature operation up to 280K.