MEASUREMENT OF THE DIRECT ENERGY-GAP OF AL0.5IN0.5P - IMPLICATIONS FOR THE BAND DISCONTINUITY AT GA1-XINXP/ALYIN1-YP HETEROJUNCTIONS

In a recent paper [Phys. Rev. B 48, 18031 (1993)], Patel and co-workers described hydrostatic-pressure-dependent photoluminescence measurements performed on Ga0.47In0.53P/Al0.5In0.5P multiple quantum wells. They determined directly a valence-band offset of 0.24+/-0.05 eV from the energy difference between the indirect transition in the barrier and the transition from X states in the barrier to hh1 valence-band states in the quantum well, when extrapolated to zero pressure. The conduction-band offset was then indirectly determined to be 0.26 eV from the total-band discontinuity of the system, assuming a value of 2.45 eV for the (low temperature) lowest-energy direct gap of Al0.5In0.5P. This yields a band-offset ratio, Delta E(c):Delta E(v), of 52:48. Here, we present evidence that the (5 K) direct gap of the Al0.5In0.5P barrier is similar to 2.685 eV, which results in a revised band-offset ratio of 67:33, similar to recent values determined for Ga1-xInxP/(AlyGa1-y)(0.5)In0.5P heterojunctions.