Electrical characteristics of symmetric, compositionally graded triangular heterostructure diodes grown by molecular beam epitaxy

Abstract

Symmetric, triangular barriers with alloy induced heights of about 250 meV and between 40 and 150 nm thick have been grown in AlGaAs by linear ramping of composition in a conventional solid-source molecular beam epitaxy system and their current–voltage characteristics measured between 55 to 300 K. Characteristics are also calculated, with electron tunneling contributions included by a finite-element Wentzel–Kramers–Brillouin approach which allows an arbitrary composition and/or doping profile to be modeled. Theory and experiment generally coincide, increased tunneling contributions are detected at lower temperatures and in narrower barriers, principally through a reduction in barrier height and an increase in ideality factor. The incorporation of dopants in the barrier produces an ionized-donor space charge with a consequent reduction in real barrier height and width, while anomalous behavior in some samples seems to be associated with trapping within the barrier.