Quantum heterostructures for micro- and opto-electronics

Space-charge limited ballistic transport of quantized holes in a short doped p-GaAs quantum well (QW) causes a generation of current oscillations. This generation is a result of a negative effective mass region in the hole dispersion relation. An oscillation frequency, which is in the subterahertz or terahertz ranges, depends on the parameters of the diode structure with the quantum well as a base. It is determined by the longitudinal mode of the selftuning plasma cavity in the diode base which depends on a Fermi-energy of the holes emitted by the p⁺-anode and cathode into the base. The best oscillation generation regime is achieved at some optimum value of the Fermi-energy. The generation of terahertz radiation (0.5÷1.5 THz) with efficiency about 1% is easy to achieve in p-GaAs QWs of 0.1÷0.5 μm length, about 10 nm width, and 10¹¹ cm^-2 doping. A double quantum well segment (DQWS) formed by the tunnel contact between a current conducting quantum well channel and a segment of a similar quantum well represents a resonator transparent for carriers with particular wave vectors and opaque for the others. As a result short n⁺nn⁺ diodes with the DQWS in the conducting channel display saw-tooth shaped current voltage characteristics with repeated N-shaped (or Z-shaped) parts. Such devices can be used for high frequency generation.