CAPTURE BARRIER AND THE IONIZATION ENTROPY OF THE DX CENTER IN SE-DOPED ALXGA1-XAS

Recently there has been clear evidence that local alloy disorder splits the DX center in multiple levels. This effect is observed by deep-level transient spectroscopy (DLTS) from different thermal emission rates for the multiple levels in Al(x)Ga(1-x)As We report for the first time the simultaneous measurement of two capture barrier and two ionization entropies for the DX center in Se-doped Al(x)Ga(1-x)As. The Al(x)Ga(1-x)As was grown by metalorganic chemical vapor deposition at two different alloy compositions (x = 0.19 and 0.23). We obtained the capture rates from a DLTS experiment by simultaneously monitoring the two transient signals while changing the filling pulse width. The capture rates show exponential temperature dependence from which the thermal capture barriers are extracted. Together with the emission rate values the ionization entropy is calculated after modifying the appropropriate equations for a degenerate semiconductor (N(D) > 1 x 10(17) for AlGaAs). The results are discussed in the context of other published values.