Electrical properties of BeMgZnO/ZnO heterostructures with high-density two-dimensional electron gas

摘要

Accumulation of non-equilibrium hot longitudinal optical (LO) phonons limits the electron drift velocity for electronicdevices operating under high electric field. Ultrafast decay of non-equilibrium hot LO-phonons can take place viaplasmon-LO phonon resonance, which leads to desired fast electron energy relaxation and hence high electron driftvelocity and optimum device operation. The need for velocity motivates us to create heterostructures with 2DEGdensities close to the plasmon-LO phonon resonance region. By incorporating a few percent Be into the BeMgZnObarrier layer to switch the strain in the barrier from compressive to tensile, we have achieved 2DEG densities over awide range in Zn-polar BeMgZnO/ZnO heterostructures with moderate Mg content (below 30%) grown by molecularbeam epitaxy (MBE). We have obtained an electron mobility of 250 cm~2/Vs at room temperature (293 K) and 1800cm~2/Vs at 13 K in a Be_(0.02)Mg_(0.26)ZnO/ZnO heterostructure. Via capacitance-voltage (CV) spectroscopy, we have exploredthe depth profiles of the apparent carrier density for samples grown under different conditions. In this paper, thecorrelations between electrical properties and MBE growth parameters of Zn-polar BeMgZnO/ZnO heterostructures arediscussed.