Asymmetrical current conduction across a 50 A thick aluminium gallium nitride polarisation barrier

Rectification by a 50 Å (5 nm) thick aluminium gallium nitride (AlGaN) polarisation barrier with maximum voltage swing of 27 V is demonstrated. In order to achieve a large voltage swing, the device is constructed with a 3000 Å (300 nm) thick undoped gallium nitride (GaN) space charge layer adjacent to the barrier to enable a large voltage drop before the advent of impact ionisation breakdown. The spontaneous and piezoelectric polarisation discontinuities at the AlGaN/GaN interfaces determine the band profiles and the thermally assisted tunneling flux of electrons through the barrier. The 3.24 MV cm−1 electric field across the 50 Å thick barrier at low bias enables efficient tunneling of electrons, despite the large effective electron mass of 0.19. The effective barrier seen by electrons changes from triangular to trapezoidal for one direction of bias and enhances the asymmetry effect. The demonstrated device characteristics show that wide band-gap polarisation barriers can potentially be used as the basic components of high-power microwave limiters.