Hot electron transistors grown by MOCVD

Abstract

Using AlGaAs GaAs hot electron transistors (HETs) grown by MOCVD (metalorganic chemical vapor deposition), we have studied the injected hot electron transport during traversal in the doped GaAs base-layer. An anomalous peak and shoulder in the transfer ratio α (=Ic/Ie) vs. emitter-voltage relation were seen in a HET having a lightly doped base, and they were attributed to the onset of the intervalley scattering from Γ to L and from Γ to X band minima, respectively. With increasing electron doping density in the base layer, α decreased drastically and structures ascribed to intervalley scatterings became obscured. In addition, α depended inverse-exponentially on base thickness. It can be concluded that a strong scattering caused by conduction electrons and/or impurities is involved in the transfer process. Current gain β under the common-emitter configuration exceeded 5 and when strained GaInAs was incorporated in the base layer, β exceeded 10, showing the potentially high performance of this new material system.