Normal incident two color voltage tunable InGaAs quantum well infrared photodetectors

Abstract

By using highly doped InGaAs quantum wells, grating-free two color quantum well infrared photodetectors with large normal incidence responses have been demonstrated. Two different structures were used for different voltage tuning characteristics. The In0.3Ga0.65As/Al0.3Ga0.7As quantum wells with 3.5x10(18) cm(-3) Si doping were used to fabricated MWIR QWIP with bound to bound transition and bound to continuum transition. In0.3Ga0.7As/GaAs quantum wells with 1x10(18) cm(-3) Si doping were used to fabricate LWIR QWIP with bound to continuum transition and bound to quasi continuum transition. The MWIR QWIP and LWIR QWIP were stacked together for two-color operation. The grating-free devices were measured with normal incident infrared radiation and compared with those with surface grating. Very good responses were obtained from grating-free devices with the TE to TM response ratio around 50-35% for both wavelength ranges. Due to a higher resistance, the MWIR stack turned on at lower voltages than the LWIR stack. The voltage tuning characteristics of the two structures were studied.