Abstract
Mid-infrared light emitting diodes and quantum cascade lasers are of increasing interest due to their promising applications. They can be used in detecting and monitoring pollutant gases such as methane (CH4) and carbon dioxide (CO2). Such devices are preferred for these purposes due to their potential for high sensitivity for detecting gases, long device lifetime, and potential low-cost. Mid-infrared light emitting diodes emitting at a wavelength of 3.7 μm based on the pentanary alloy GalnAsSbP engineered to provide a favourable band structure for the suppression of non-radiative Auger recombination were investigated. Temperature dependence measurements were made to investigate the performance of these LEDs. Hydrostatic pressure measurements at room temperature and at 100 K were used to tune the band gap towards resonance with the spin-orbit splitting to investigate the influence of the hot-hole (CHSH) Auger process on LED performance. Analysis of the resulting electroluminescence showed that while Auger recombination related to hot electrons occurs, it confirms that the non-radiative Auger recombination process involving the spin-orbit split-off band (CHSH) is suppressed under ambient conditions. In order to identify the performance limitations of InGaAs/AlAs(Sb) quantum cascade lasers, experimental investigations of the temperature and pressure dependencies of the threshold current (Ith) were undertaken. Using the theoretically estimated optical phonon current (Iph) and calculated carrier leakage (Ileak) as a function of pressure the measured pressure dependence of the threshold current showed that electron scattering from the upper laser level into the L valley minima gives rise to the increase in Ith with pressure and temperature. It was found that this carrier leakage path accounts for approximately 3% of Ith at RT and is negligible at 100 K. However, it is shown that even this small leakage current causes strong temperature sensitivity of the devices and limits their maximum operating temperature.