In this communication we show that we can distinguish the absorption o
f a single quantum well from that of the substrate in a quantum well s
tructure by using photothermal deflection spectroscopy (PDS). This tec
hnique uses the phase of the PDS signal, in addition to the amplitude.
The method is applied to single and multiple quantum wells grown on I
nP substrates. (C) 1996 American Institute of Physics.