TE SUBSTITUTION IN DISORDERED DILUTE SE1-XTEX ALLOYS

Photoacoustic absorption measurements at room temperature are reported for Se1-xTex alloys in both crystalline and amorphous states for 0<x less than or equal to 0.3. The optical energy gap thus measured shows two features: (a) the gap decreases linearly as x increases with a cha nge of slope at x=0.1 for both crystalline and amorphous alloys; and ( b) the difference in the gaps corresponding to the amorphous and cryst alline phase remains remarkably constant over the entire range of x(0- 0.3) studied here. We attribute the result (a) to the onset of ''quant um percolation'' at x = 0.1, and deduce from (b) that introduction of Te apparently does not affect the structural disorder. The results are argued to yield vital information about the restrictive nature of Te substitution into host Se. (C) 1998 American Institute of Physics. [S0 003-6951(98)00243-5].