Temperature sensitivity of 1.54-μm vertical-cavity lasers with an InP-based Bragg reflector

We fabricated 1.54-μm laser diodes that employ one integrated GaInAsP-InP and one Si-SiO₂ mirror in combination with a strain-compensated GaInAsP multiquantum-well active layer. Considerable care has to be taken of the temperature performance of the devices. Here, an important parameter is the gain offset between the gain peak wavelength and the cavity resonance. This offset is related to the experimentally accessible photoluminescence (PL) offset between the PL-peak wavelength and the emission wavelength. Vertical-cavity laser (VCL) characteristics such as threshold current and quantum efficiency show an extremely sensitive dependence on this parameter. In this paper, we focus on the temperature performance of our VCL´s as a function of the cavity tuning. VCL´s designed for PL-offset values between +17 and -16 mm are fabricated and characterized, As expected, the threshold current of all lasers shows a pronounced minimum at low temperatures. The position of this minimum depends on the offset at room temperature (RT) as a parameter. However, it turns out that the minimum threshold current is not obtained by matching gain peak and cavity wavelength for that temperature. The observed behavior is described well by calculations, taking into account the temperature dependence of the optical gain, of the cavity resonance, and of the cavity losses. The model is a valuable tool to tune the lasers for example low threshold current or reduced temperature sensitivity