The temperature dependence of 1.3- and 1.5-μm compressively strained InGaAs(P) MQW semiconductor lasers

We have studied experimentally and theoretically the spontaneous emission from 1.3- and 1.5-μm compressively strained InGaAsP multiple-quantum-well lasers in the temperature range 90-400 K to determine the variation of carrier density n with current I up to threshold. We find that the current contributing to spontaneous emission at threshold I_Rad is always well behaved and has a characteristic temperature T₀ (I_Rad)≈T, as predicted by simple theory. This implies that the carrier density at threshold is also proportional to temperature. Below a breakpoint temperature T_B, we find I α n^Z, where Z=2. And the total current at threshold I_th also has a characteristic temperature T₀ (I_th)≈T, showing that the current is dominated by radiative transitions right up to threshold. Above T_B, Z increases steadily to Z≈3 and T₀ (I_th) decreases to a value less than T/3. This behavior is explained in terms of the onset of Auger recombination above T_B; a conclusion supported by measurements of the pressure dependence of I_th. From our results, we estimate that, at 300 K, Auger recombination accounts for 50% of I_th in the 1.3-μm laser and 80% of I_th in the 1.5-μm laser. Measurements of the spontaneous emission and differential efficiency indicate that a combination of increased optical losses and carrier overflow into the barrier and separate confinement heterostructure regions may further degrade T₀ (I_th) above room temperature