Ternary III - nitride alloys such as InGaN allows bandgap tuning by changing molar ratios of the binary constituents. This opens up the possibility of covering the full visible spectrum by changing In content in InGaN compounds which could be applied in developing optoelectronic devices. Growing In content or QW (quantum well) width promotes several problems such as electron hole separation due to internal electric fields, formation of point defects and dislocations, which affect carrier lifetime of the alloy. The aim of this work is to determine the relationship between carrier lifetime and cathodoluminescence wavelength in high (long carrier lifetime) and low (short carrier lifetime) quality InGaN samples.
In this work combination technique of scanning electron microscopy and cathodoluminescence in pulsed mode is used. This method enables determination of carrier lifetimes at all radiative recombination processes by analysing streak camera images of the sample at different sample points.
The results show that for short carrier lifetime InGaN samples carrier lifetime peak is red shifted in relation to cathodoluminescence intensity due to variations in both the local In composition and the QW width related to carrier localization effect in InGaN QW regions and energy band fluctuations. For bulk InGaN samples such dependency is not observed due to higher probability of nonradiative recombination at point defects and dislocations.
For long carrier lifetime InGaN samples few carrier lifetime maxima are observed which could be the result of radiation from different energy levels of QW.
Given results could be used to further analyse radiative and nonradiative mechanisms and causes at various parts of InGaN samples.