Experimental and modelling study of InGaBiAs/InP alloys with up to 5.8% Bi, and with Δso > Eg

Temperature dependent photo-modulated reflectance is used to measure the band gap E-g and spin-orbit splitting energy Delta(so) in dilute-Bi In0.53Ga0.47As1-xBix/InP for 1.2% <= x <= 5.8%. At room temperature, Eg decreases with increasing Bi from 0.65 to 0.47 eV (similar to 2.6 mu m), while Delta(so) increases from 0.42 to 0.62 eV, leading to a crossover between E-g and Delta(so) around 3.8% Bi. The 5.8% Bi sample is the first example of this alloy where Delta(so) > E-g has been confirmed at all temperatures. The condition Delta(so) > E-g is important for suppressing hot-hole-producing non-radiative Auger recombination and inter-valence band absorption losses and so holds promise for the development of mid-infra-red devices based on this material system. The measured variations of E-g and Delta(so) as a function of Bi content at 300 K are compared to those calculated using a 12-band k.p Hamiltonian which includes valence band anti-crossing effects. The E-g results as a function of temperature are fitted with the Bose-Einstein model. We also look for evidence to support the prediction that E-g in dilute bismides may show a reduced temperature sensitivity, but find no clear indication of that.