Quantum Phenomena in Semiconductor Structures
Rept. no. 1 (Annual), Oct 1985-Oct 1986; Interim rept. no. 4-6, Oct 1986-Apr 1988,
CAMBRIDGE UNIV (UNITED KINGDOM) CAVENDISH LAB
Pagination or Media Count:
We have commenced experiments aimed at producing a metal pattern on the AlGaAs of an AlGaAs-GaAs modulation doped heterojunction. This will enable us to investigate details of the transport when the effective sample length is considerably less than the scattering mean free path. Many of the proposed experiments of this grant concern one dimensional effects and we have concentrated during this last period on the energy levels in narrow modulation doped electron channels in AlGaAs-GaAs heterojunctions. Previously we demonstrated the existence of disorder-induced, one-dimensional conductivity corrections in a narrow-channel electron gas within a split-gate GaAsAlGaAs heterojunction field-effect transistor. At temperatures such that the phase- relaxation inelastic length and the interaction length are greater than the channel width, the quantum corrections to the conductivity become one dimensional. We have now investigated the effects of a large, transverse, magnetic field on the conductivity when the channel is narrow. A WKB calculation was performed which shows that a magnetic-field-induced depopulation of the one- dimensional subbands occurs. The mobility in this system is much higher than in other quasi 1D systems so that lifetime broadening of electronic subbands approx equal Tau is sufficiently small for subband depopulation to be directly observed as structure in the magnetoconductance. Here Tau is the elastic lifetime.
- Electrical and Electronic Equipment
- Quantum Theory and Relativity
- Solid State Physics