InGaAsSb p-n heterojunctions studied by photoluminescence and photoacoustic spectroscopies for photovoltaic applications

By using the liquid phase epitaxy (LPE) technique we report the growth of p-n InGaAsSb layer structures on top of (100) GaSb substrates under lattice-matched conditions. The 1st layer was an n-type InGaAsSb (Te-doped), whereas the 2nd layer was a p-type InGaAsSb (Zn-doped). The Zn-doped InGaAsSb layer in the heterostructure was characterized using microRaman spectroscopy, the photoacoustic (PA) technique, and the low temperature photoluminescence (PL) spectroscopy. From the Raman spectra we found the presence of the LO GaAs-like, the TO (GaSb+InAs) and the TO and LO InSb modes with energies that agree with reported results for this type of heterostructures. The PA characterization shows that for those samples with lower Zn-doping levels, the non-radiative recombination times are higher indicating better crystalline quality. The photoluminescence (PL) spectra showed bands centered at 2015, 1980 and 2120 nm for the samples doped with 0.23, 0.54 and 0.89 mg of Zn in the melt solution. For the first two samples we associate the PL bands to exciton and donor-to-valence band recombination, whereas for the sample with higher Zn doping, the broader PL band would come from defect-related transitions.