Percolation of carriers through low potential channels in thick AlxGa1-xAs (x<0.35) barriers.

摘要: We study by photoluminescence excitation the heretofore unsolved puzzle of a significant charge transfer over thick ~100 to 1500 A ! AlxGa12xAs barrier in GaAs/AlxGa12xAs asymmetric double quantum wells, which normally considered tunneling cannot account for. This phenomenon is completely general, observed all samples grown under standard growth conditions ~;600 °C!, that originated from many different sources. The existence such leakage also confirmed time-resolved experiments. However, when alloy replaced an equivalent GaAs/AlAs digital alloy, or AlAs, leak largely disappears. In addition, GaAs separating two shallow xGa12xAs wells permits only relatively small transfer. has weak dependence on thickness at x50.3, but very strong function x around x50.3. argue there no way explain phenomena simultaneously other than intrinsic structural inhomogeneities alloy. Essentially, may exist low potential channels created microscopic clustering like molecules, through percolationlike transport occurs. picture supported three-dimensional quantummechanical model calculation. Our work pins down dynamical implications partial ordering and related semiconductor ternary alloys. scope this paper exclusively for barriers ( x,0.35) does not include still non-negligible homogeneous as GaAs, AlAs/GaAs alloys, (x.0.35). contend these thick, be owing mechanisms dipole-dipole transfer, photon reabsorption, nonequilibrium distribution carriers, polariton are unrelated conventional tunneling. @S0163-1829~96!02144-3#