InP/InGaAs heterojunction phototransistor operating at wavelengths above 2 μm realized using strained InAs/InGaAs multiquantum well absorption layer

A new infrared photodetector has been developed that provides a high responsivity and a low dark current. The device consists of a heterojunction phototransistor (HPT) with a strained InAs/InGaAs multiquantum well (MQW) absorption layer. The insertion of a thick strained InAs well into the low electric field region of the collector makes it possible to maintain a large excitonic effect, and a high absorption coefficient is obtained even at a wavelength as long as 2.3μm. The photocurrent generated in the MQW absorption layer is amplified by the current gain, resulting in a high responsivity of more than 10 A/W. In addition, the small volume of the MQW in the low electric field region provides a low dark current even at room temperature.