Internal field effects on the lasing characteristics of InGaN/GaN quantum well lasers

Abstract

A theoretical investigation of InxGa1−xN/GaN single quantum well lasers with x in the range 0.05⩽x⩽0.3 is carried out via self-consistent Schrödinger–Poisson calculations in the effective mass approximation in order to quantify the adverse effects of the internal electric field on the lasing characteristics of these heterostructures. We find a nonzero optimum internal field value that minimizes the threshold current density Jth, and whose amplitude depends on the quantum well width, In content, and cavity losses. We demonstrate that the complete elimination of the internal field in In0.2Ga0.8N/GaN blue laser diodes with typical cavity losses should result in a decrease in Jth by as much as a factor of 4. Furthermore, for a wide range of In contents and cavity losses, we find that the optimum well width that minimizes Jth ranges between 2.5 and 4 nm. Finally, we show that the longest lasing wavelength that can be achieved from an InGaN/GaN quantum well laser is in the range of 480–500 nm depending on cavity losses.