Abstract

Lasers emitting in the 2-3μm mid-infrared spectral window have numerous applications. Non-radiative processes such as Auger recombination and carrier leakage cause increased threshold current density (J_th) with increasing temperature and as a result, limit their maximum operating temperature for lasers operating in this wavelength range [1]. In type-I interband devices, the band gap determines the wavelength, hence investigating the effects of band gap shift on the device properties provides a means of optimisation. In this work, temperature and hydrostatic pressure have been used independently to tune the bandgap of GaInAsSb type-I edge emitting lasers. The dependence of J_th, Auger current (J_Auger) and radiative current (J_rad) on the band gap of these devices is presented (Fig. 1a). Results show that by applying pressure, the T₀ of the 2.6μm device increases from 37±5K up to ~53±5K (Fig.1b) when operating at 2.3μm under pressure. This value is similar to the as-grown 2.3μm for which T₀ =59±5K (Fig. 1a). However, J_th is ~25% higher compared to an as-grown 2.3μm device. This difference is due to the fact that the as-grown 2.3μm device maintains larger band offsets than the pressure-tuned 2.3μm device. Hence, the reduced J_th of the as-grown device may be associated with a lower carrier leakage current. Whilst the larger band offset helps reduce J_th it makes little difference to its temperature sensitivity in these type-I GaInAsSb/GaSb devices. This indicates that further optimisation of the band offset would bring little benefit in terms of T₀ and that reducing the Auger process would be of much larger benefit. We also show that non-pinning of the carrier density above threshold and intervalence band absorption cause the external differential efficiency of these devices to decrease with increasing temperature.

© 2013 IEEE