Abstract
Herein, the optical field distribution and electrical property improvements of the InGaN laser diode with an emission wavelength around 416 nm are theoretically investigated by adjusting the relative thickness of the first or last barrier layer in the three In0.15Ga0.85N/In0.02Ga0.98N quantum wells, which is achieved with the simulation program Crosslight. It was found that the thickness of the first or last InGaN barrier has strong effects on the threshold currents and output powers of the laser diodes. The optimal thickness of the first quantum barrier layer (FQB) and last quantum barrier layer (LQB) were found to be 225 nm and 300 nm, respectively. The thickness of LQB layer predominantly affects the output power compared to that of the FQB layer, and the highest output power achieved 3.87 times that of the reference structure (symmetric quantum well), which is attributed to reduced optical absorption loss as well as the reduced vertical electron leakage current leaking from the quantum wells to the p-type region. Our result proves that an appropriate LQB layer thickness is advantageous for achieving low threshold current and high output power lasers.
Highlights
InGaN-based multi-quantum well (MQW) laser diodes (LDs) have drawn much attention in recent years due to their potential as the light sources in the applications of high-density optical storage systems, laser printing, full-color displays, small portable projector, among the others [1,2,3,4,5,6,7,8,9,10]
Even if more optical fields are distributed inside the first quantum barrier layer (FQB) or LQB layer, the optical absorption loss further decreases, but the optical limit factor (OCF) may be reduced by the shift of the peak position of the optical field [28]
A series of In0.15Ga0.85N/In0.02Ga0.98N MQW laser diodes (LDs) with different barrier layers are investigated with the simulator Crosslight
Summary
InGaN-based multi-quantum well (MQW) laser diodes (LDs) have drawn much attention in recent years due to their potential as the light sources in the applications of high-density optical storage systems, laser printing, full-color displays, small portable projector, among the others [1,2,3,4,5,6,7,8,9,10]. The material composition, number, and thickness of the multiple quantum well (WQW) in the active region are crucial structural parameters for optimizing the structure of LD because they directly affect the optical and electrical properties of the device. The effect of QW number on the performance of MQW LDs has been studied both theoretically and experimentally [11,12,13], which indicates that the blue-violet laser (emission wavelength between 392 nm and 420 nm) with two InGaN wells could obtain the lowest threshold current when the band gap ratio is 7/3. The relative thickness of the first or last barrier layers in the three In0.15Ga0.85N/In0.02Ga0.98N quantum wells laser diode, are designed and optimized to enhance the optical field distribution into the MQW while reducing the optical absorption loss. By redesigning the barrier layer, the comparison between their optical and electrical characteristics (especially leakage current) are analyzed and compared with the theoretical simulation results
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