Two types of Si pnp punch-through BARITT diodes are fabricated and the d.c. and small-signal characteristics are studied both experimentally and theoretically. The d.c. solution of carrier-density and electric field distributions was numerically obtained with temperature- and field-dependent drift velocity for two types of diodes; uniform and non-uniform doping profiles. The calculated voltage-current curves were in good agreement with the measured ones from 210 K to 373 K. This agreement implies that the injection mechanism is not thermionic emission but diffusion-limited. Small-signal impedance was derived as functions of injection conductivity and transit-time-dependent space-charge impedance; the injection conductivity was given by perturbation of the d.c. solution and compared with other published theories. The present theory is applicable to a BARITT diode with non-uniform doping. The theory also succeeded in explaining the effect of self-heating. Because of neglect of the velocity-modulation and a.c. diffusion components, the theory overestimates the magnitude of negative resistance when a diode has low doping density (1015/cm3) in the emitter junction. Some predictions were made on effects of temperature, a doping profile and a velocity-field curve on the negative resistance by using the derived formula. As an example, the negative resistance of a GaAs BARITT diode is also predicted.

We have systematically studied the characteristics of Si doping in GaAs grown on (311)A GaAs substrates by molecular beam epitaxy. The growth temperature dependence of Si doping has been investigated. It is found that the conduction-type sharply changes from p-type to n-type with decreasing growth temperature at a critical temperature of 430-480. The highest hole density obtained for uniformly doped layers was 1.51020 cm-3, while for δ-doped layers the sheet hole density as high as 2.61013 cm-2 was achieved. This is the highest hole density ever reported for δ-doped GaAs.