Influence of Depletion Fields on Photoluminescence of n-Doped InGaN/GaN Multiple Quantum Well Structures

Abstract

We report on a detailed study of low temperature photoluminescence (PL) in In x Ga 1-x N multiple quantum wells (MQWs) with x in the range 0.1 and highly Si-doped barriers of In 0.01 Ga 0.99 N. The entire MQW structure was grown at 800 °C. One sample with 3 QWs of width 3.5 nm and barriers of width 10.5 nm had the MQW in the depletion region of the outer surface. Two PL peaks were observed, one QW exciton from the QW closest to the GaN buffer, one lower energy peak related to a 2DEG at the interface to the GaN buffer layer. In a second similar sample, 5 QWs of width 3 nm and with 6 nm highly Si-doped In 0.01 Ga 0.99 N barriers the MQW was placed in the n-side depletion region of a pn-junction, i.e. a complete LED structure with semitransparent top metallisation. Two PL peaks are observed also in this case, of similar origin as described above. With forward bias, this structure shows lower-energy PL emission, indicating the gradual activation of the other QWs closer to the pn-junction. At high forward bias the low-energy part of the PL spectrum becomes similar to the electroluminescence (EL) spectrum.