The Effect of Pressure and Temperature on AlGaInP and AlGaAs Laser Diodes

Abstract

InGaP/AlGaInP lasers (emitting from 630 to 690 nm) and GaAs/ AlGaAs lasers (emitting at 780 nm) were studied under hydrostatic pressure up to 20 kbar and at temperatures from 240 to 300 K. The electrical characteristics, the power-current dependencies and the emission spectra were measured. The emission spectra shifted in agreement with the pressure/temperature variation of the band gaps in active layers of the laser. Since at high pressure the Γ-X separation in the conduction band is strongly reduced (both in AlGaInP and AlGaAs), the dominant loss mechanism of the lasers is the electron leakage to X minima in the p-claddings. This, in turn, leads to high sensitivity of threshold currents to temperature. The dependence of threshold currents on pressure and on temperature is in good agreement with the simple theoretical analysis taking into account the carrier leakage and the radiative and nonradiative recombination. Better agreement between the theory and the experiment is obtained assuming drift rather than diffusion leakage. This indicates that threshold currents could be further reduced if the p-doping is improved in the claddings.