MBE growth of high performance very long wavelength InGaAs/GaAs quantum well infrared photodetectors

We report on the effects of two different molecular beam epitaxy growth modes on the performance of In_0.14Ga_0.86As/GaAs quantum well infrared photodetectors (QWIPs). The performance of quantum well (QW) materials are characterized by photoluminescence (PL), x-ray diffraction, and high resolution transmission electron microscope, and a systematic photoelectric characterization is carried out for these InGaAs/GaAs QWIPs. The results indicate that the introduction of continuous low temperature growth can effectively reduce In atom interdiffusion while maintaining the higher PL intensity. QWIPs grown by the low temperature method show the bound-to-bound intraband transition mode as initially designed, whereas the high temperature during the growth makes the operating mode of the device changing to bound-to-quasi continuous mode, which affects the performance of the quantum well infrared photodetectors. Compared with InGaAs/GaAs QWIP fabricated by the temperature-changed growth method, the peak responsivity of the low-temperature grown sample is increased by a factor of 38 and reaches 5.67 A W^-1 at 20 K, indicating high responsivity of InGaAs/GaAs QWIP. The reason is attributed to the pronounced increase of photoconductive gain in the device with the B-B working mode. Furthermore, the background limited performance temperature (T _BLIP) of low-temperature grown QWIPs is improved by ∼10 K.