Band-edge aligned quaternary carrier barriers in InGaAs-AlGaAs high-power diode lasers for improved high-temperature operation

A new type of band-edge aligned carrier barriers is introduced into InGaAs-AlGaAs single quantum-well (SQW) high-power diode laser structures in order to prevent thermionic emission and the overflow of carriers at elevated operating temperatures. These barriers, which are located in the direct vicinity of the active zone of the laser, are undoped to avoid free-carrier absorption. An InGaAs-AlGaAs SQW laser structure with a 10-nm-thick AlGaAsSb electron-blocking layer on the p-side of an In(0.2)Ga(0.8)As quantum well was realized. The composition of this layer was adjusted so that its valence-band edge matches that of the adjacent AlGaAs waveguide layer. This is to prevent any additional voltage drop or series resistance due to the injection of holes into the quantum well through the electron blocking layer. These lasers show a high characteristic temperature T(0) of about 225 K for 1500-µm-long as-cleaved devices, which is about 60 K higher than the same laser structure without the blocking layer. Simultaneously low internal losses (alpha(i)~1.5 cm(exp -1) at 20°C) and high internal quantum efficiencies (n(i)~93 % at 20°C) are achieved. No additional voltage drop or series resistance was measured. The higher temperature stability is mainly attributed to the suppression of carrier leakage and a reduced free-carrier absorption at elevated temperatures.