Impact of ultra-thin quaternary capping on modulation doped p-i-p quantum dots (InAs/GaAs) based infrared detector

In this study, we demonstrate the device performance of modulation doped InAs/GaAs p-i-p QDIP (device A) and the effect of thin 1 nm quaternary (InAlGaAs) capping on the same heterostructure (device B). The ground state emission peak at 9 K from photoluminescence spectroscopy was measured at 1055.1 nm and 1046.4 nm for sample A and B, respectively. The measured dark current densities at 75 K for an applied bias of -1 V were 1.079 A/cm⁻² and 0.038 A/cm⁻² for device A and B, respectively. The fabricated single pixel detectors from device A exhibited emission peak in short wave infrared regime whereas whereas device B exhibited a multicolour spectral response from short wave (SWIR) to mid wave infrared (MWIR) region. The measured spectral peaks at low temperature were at 2 and 2.39 μm for device A and at 2.013, 2.49, 3.49 and 4.36 μm with a dominant peak in SWIR region for device B. Both the devices exhibited spectral response peak up to 75K with a responsivity of 0.832 A/W for device A compared to that of 0.545 A/W for device B at -2.5V bias. Tunability in detection peak with improvement in device performance was achieved by incorporating additional quaternary capping.