The efficiency droop in $\mathrm{GaInN}∕\mathrm{GaN}$ multiple-quantum well (MQW) light-emitting diodes is investigated. Measurements show that the efficiency droop, occurring under high injection conditions, is unrelated to junction temperature. Furthermore, the photoluminescence output as a function of excitation power shows no droop, indicating that the droop is not related to MQW efficiency but rather to the recombination of carriers outside the MQW region. Simulations show that polarization fields in the MQW and electron blocking layer enable the escape of electrons from the MQW region and thus are the physical origin of the droop. It is shown that through the use of proper quaternary AlGaInN compositions, polarization effects are reduced, thereby minimizing droop and improving efficiency.

The authors analyse the performance and device physics of nitride laser diodes that exhibit the highest room-temperature continuous-wave output power. The analysis is based on advanced laser simulation. The laser model self-consistently combines band structure and free-carrier gain calculations with two-dimensional simulations of wave guiding, carrier transport and heat flux. Material parameters used in the model are carefully evaluated. Excellent agreement between simulations and measurements is achieved. The maximum output power is limited by electron leakage into the p-doped ridge. Leakage escalation is caused by strong self-heating, gain reduction and elevated carrier density within the quantum wells. Built-in polarisation fields are found to be effectively screened at high-power operation. Improved heat-sinking is predicted to allow for a significant increase of the maximum output power.

We analyze the high-temperature continuous-wave performance of 1.3-/spl mu/m AlGaInAs/InP laser diodes grown by digital alloy molecular-beam epitaxy. Commercial laser software is utilized that self-consistently combines quantum-well bandstructure and gain calculations with two-dimensional simulations of carrier transport, wave guiding, and heat flow. Excellent agreement between simulation and measurements is obtained by careful adjustment of material parameters in the model. Joule heating is shown to be the main heat source; quantum-well recombination heat is almost compensated for by Thomson cooling. Auger recombination is the main carrier loss mechanism at lower injection current. Vertical electron escape into the p-doped InP cladding dominates at higher current and causes the thermal power roll-off. Self-heating and optical gain reduction are the triggering mechanisms behind the leakage escalation. Laser design variation is shown to allow for a significant increase in the maximum output power at high temperatures.

III-nitride light-emitting diodes (LEDs) suffer from a severe efficiency reduction with increasing injection current (droop). Auger recombination is often seen as primary cause of this droop phenomenon. The corresponding Auger recombination coefficient C is typically obtained from efficiency measurements using mathematical models. However, C coefficients reported for InGaN active layers vary over two orders of magnitude. We here investigate this uncertainty and apply successively more accurate models to the same efficiency measurement, thereby revealing the strong sensitivity of the Auger coefficient to quantum well properties such as electron-hole ratio, electric field, and hot carrier escape.