Gamma -X intervalley tunnelling in a GaAs/AlAs resonant tunnelling diode under uniaxial stress

Longitudinal uniaxial stress (O<S<36 kbar) at 300 K and 77 K was used to experimentally examine intervalley tunnelling processes in a GaAs/AlAs resonant tunnelling diode (RTD) by lowering quasibound states confined in AlAs X-point quantum wells with respect to the Gamma -point conduction band profile. Intervalley resonances were observed that arose from tunnelling through: (i) large effective mass longitudinal X-states, (ii) a small-mass transverse X-state, and (iii) longitudinal X-states in AlAs aligned with the Gamma -point ground state confined in the adjacent GaAs quantum well, resulting in a resonance with a bias voltage position that increased (decreased) with increasing stress for X-states in the emitter (collector) AlAs layer. At 77 K, intervalley tunnelling can provide resonances of magnitude comparable with the intravalley Gamma resonance. Intervalley resonances remained observable in the differential conductance at 300 K. Self-consistent calculations of device characteristics agreed with the data and established voltage-stress domains for all possible intervalley resonances in the RTD.

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