Carbon doping of GaAs grown by molecular beam epitaxy has been obtained for the first time by use of a heated graphite filament. Controlled carbon acceptor concentrations over the range of 1017–1020 cm−3 were achieved by resistively heating a graphite filament with a direct current power supply. Capacitance-voltage, p/n junction, and secondary-ion mass spectrometry measurements indicate that there is negligible diffusion of carbon during growth and with post-growth rapid thermal annealing. Carbon was used for p-type doping in the base of Npn AlGaAs/GaAs heterojunction bipolar transistors. Current gains greater than 100 and near-ideal emitter heterojunctions were obtained in transistors with a carbon base doping of 1×1019 cm−3. These preliminary results indicate that carbon doping from a solid graphite source may be an attractive substitute for beryllium which is known to have a relatively high diffusion coefficient in GaAs.

SummaryLight-induced interfacial electron transfer from two p-InP electrodes differing in the amount of majority carrier doping to a number of electron relays (R) dissolved in aqueous solution was investigated. The material with the lower carrier density (0.71 x lo'* cmP3) exhibited much better wavelength response and quantum yield for electron transfer than the electrode doped with 2.3 x 10l8 cm-3 charge carriers. Using cobalt (111) sepulcrate, Co (~ep)~', as an electron relay a polychromatic light to electrical energy conversion efficiency of 18% was obtained. The potential of this relay for use in a regenerative photoelectrochemical cell is briefly discussed.Introduction. -Interfacial electron transfer between semiconductor electrodes and electrolytes plays a primordial role in light-energy conversion devices [ 11. In the case of p-type semiconductors the transfer involves electrons (ee,), promoted by band-gap excitation to the conduction band, which reduce an acceptor (electron relay, R) dissolved in solution (Eqn. 1).

Der lichtinduzierte Grenzflächenelektronentransfer von 2 p‐InP‐Elektroden, die sich hinsichtlich der Majoritätsträgerdotierung unterscheiden, auf eine Reihe von Elektronenrelais in wäßriger Lösung wird untersucht.