Experimental and modelling study of InGaBiAs/InP alloys with up to 5.8% Bi, and with ∆(so) > E-g

Abstract

Temperature dependent photo-modulated reflectance is used to measure the band gap Eg and spin-orbit splitting energy ∆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 (~2.6 µm), while ∆so increases from 0.42 to 0.62 eV, leading to a crossover between Eg and ∆so around 3.8% Bi. The 5.8% Bi sample is the first example of this alloy where ∆so > Eg has been confirmed at all temperatures. The condition ∆so > Eg 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 Eg and ∆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 Eg results as a function of temperature are fitted with the Bose-Einstein model. We also look for evidence to support the prediction that Eg in dilute bismides may show a reduced temperature sensitivity, but find no clear indication of that.