EXPERIMENTAL-DETERMINATION OF THE CONDUCTION-BAND OFFSET AT GAAS GA1-XALXAS HETEROJUNCTIONS WITH THE USE OF BALLISTIC ELECTRONS/

The conduction-band offset Delta E(c) at GaAs/Ga1-xAlxAs heterojunctio ns has been measured by observing radiative recombination of electrons , injected ballistically from Ga1-xAlxAs into GaAs, with accepters in GaAs. Additionally, the total band-gap energy difference Delta E(g) be tween Ga1-xAlxAs and GaAs was measured with the use of photoluminescen ce, permitting a determination of the conduction-band offset coefficie nt Q(c) = Delta E(c)/Delta E(g). The measurements were carried out for various values of the mole fraction x of aluminum in the Ga1-xAlxAs a lloy, up to x=0.53. In the direct band-gap region (i.e.,x < 0. 39), Q( c) is constant and equal to 0.69. Above x = 0.39, Q(c) decreases stead ily with increasing x.