Influence of Si doping of GaN layers surrounding InGaN quantum wells on structure photoluminescence properties

In this work, the influence of Si doping position on the photoluminescence (PL) properties of InGaN/GaN quantum wells (QWs) is studied. A set of samples with different positions of Si doping with respect to the multi quantum well (MQW) active region was prepared and studied by PL, SIMS and AFM and structure band alignments were simulated. Based on our experiments and band structure simulations, we show that the dominant influence of Si doping is in modification of the tilt of the band structure. However, the minor influence of lower dislocation density or unintentional doping of a few lowest QWs in the case of a Si doped buffer layer cannot be excluded. A probable origin of the defect band luminescence and its high sensitivity to the band structure tilting is explained. Based on gained understanding, proper Si doping position for particular applications is suggested. In the case of LED structures, the n-type buffer layer and p-type capping layer help improve the emission efficiency. In the case of an InGaN/GaN MQW structure designed for scintillators, the n-type doping immediately under the MQW region is not required, since it strongly increases the QW defect band luminescence which becomes dominant in the spectrum.