Abstract
The carrier-transport characteristics of quaternary AlInGaN heterosystems are studied in-depth using photoluminescence measurements. Based on Singh's model, a higher degree of disorder in quaternary AlInGaN heterostructures is observed to manifest not only the extension of static microbarrier width, but also the enhancement of carrier localization effects. To provide a clear picture of the random configuration of the carriers photogenerated in quaternary AlInGaN heterosystems, the thermodynamic quantities, i.e., the transition enthalpy ΔH and the transition entropy ΔS, describing the spontaneous fluctuations in the irreversible generation-recombination processes increased with temperature. It is found that the anomalous temperature-dependent phenomena can be attributed to the carrier-thermalization processes. The narrow interlayer distance of an AlInGaN system facilitates thermally excited carrier redistribution. However, due to the inhibition of photocarrier transfers, AlInGaN heterostructures with wider interlayer spacing exhibit more temperature insensitivity.