GaAs and GaN Based High Operating Temperature Spin Split-off Band Infrared Detectors

Recently developed high operating temperature (up to 330 K) GaAs/AlGaAs detectors responding in the 3-5 mu m wavelength range and based on split-off (SO) transitions followed by escape by scattering to the light/heavy hole(LH/HH) band or by direct quantum mixing of the states offer a viable alternative to present day detectors operating at cryogenic temperatures. This paper presents a theoretical model to predict the response of SO detectors. The model calculates the dark current and illuminated currents from the photoabsorption, carrier escape, and transport, explaining the experimental response. Using this model, different strategies to improve the performance of the GaAs based SO detectors are presented. A graded barrier improves the performance by reducing the space charge build up, and the double barrier resonant structure by enhanced escape of holes from the SO to the light/heavy hole bands by bringing the two bands into resonance. A detailed analysis of the effect of detector parameters on responsivity and D* is made. The change of material system to GaN/AlGaN should extend the response to longer wavelengths (THz) as its zinc blende and wurtzite crystal structures have SO transition energies of 20meV and 8meV respectively. Experimental measurement of SO absorption in GaN and potential THz detector designs are discussed.