METAL-INSULATOR-TRANSITION IN ALXGA1-XAS/GAAS HETEROSTRUCTURES WITH LARGE SPACER WIDTH

Analytical results are presented for the mobility of a two-dimensional electron gas in a heterostructure with a thick spacer layer-alpha. Due to multiple-scattering effects a metal-insulator transition occurs at a critical electron density N(c) = N(i)1/2/(4-pi-1/2-alpha) (N(i) is the impurity density). The transport mean free path l(t) (calculated in Born approximation) at the metal-insulator transition is l(c)(t) = 2-alpha. A localization criterion in terms of the renormalized single-particle mean free path l(sr) is presented: k(Fc)l(c)(sr) = (1/2)1/2 (k(Fc) is the Fermi wave number at the critical density). I compare the theoretical results with recent experimental results found in AlxGa1-xAs/GaAs heterostructures with large spacer width: 1200 < alpha < 2800 angstrom. Remote impurity doping and homogeneous background doping are considered. The only fitting parameter used for the theoretical results is the background doping density N(B) = 6 x 10(13) cm-3. My theory is in fair agreement with the experimental results.