GaInAsP/InP vertical-cavity surface-emitting laser for 1.5-μm operation

Long-wavelength vertical cavity surface emitting lasers (VCSELs) operating in the 1.3μm to 1.5μm wavelength range are ideal light sources for optical fibre communication applications. However, a number of problems have hindered progress in the development of cost-effective long wavelength VCSELs. These are (a) intrinsically high non-radiative losses, (b) difficulty in fabricating highly reflecting mirrors, lattice-matched to InP, and (c) the disparity between the predicted and observed temperature dependence of the operation of the devices. In this report we present the results of our studies concerning the pulsed operation of a bulk GaInAsP/InP VCSEL fabricated at BT laboratories. The device is tailored to emit at around 1.5 μm at room temperature. The structure has a 45 period n-doped GaInAsP/InP bottom Distributed Bragg Reflector (DBR), and a 4 period Si/Al 2 O 3 dielectric top reflector. Spectral electroluminescence (EL) from a 16 μm diameter window is measured in the pulsed injection mode. Device parameters are recorded in the temperature range between 90 K and 240K. Threshold current exhibits an approximate parabolic temperature dependence with a broad minimum of J th = 13.2 kA cm -2 , at temperatures between 170K and 195K. Temperature dependence of the threshold current is compared with the theoretical calculations which consider radiative transitions with and without k-selection. Best agreement with the experimental results is obtained when a partial k- selection model, with an energy broadening of about 4.4 meV, is used in the calculations.