Halbleiteranordnung mit mindestens einem in Durchlassrichtung betriebenen p-n-UEbergang, insbesondere Transistor

906,036. Semi-conductor devices. SIEMENS & HALSKE A.G. Sept. 4, 1959 [Sept. 5, 1958], No. 30278/59. Class 37. A semi-conductor device having a forward biased PN junction between an emitter and base zone is so designed that the minority carrier concentration is effectively constant in a region extending into the emitter zone from the junction. A surface portion of the emitter zone is treated to reduce the recombination velocity and provided with one or more ohmic contacts covering only a small portion of the emitter zone surface. In one embodiment, in which the emitter zone is much thinner than the minority carrier diffusion length, the effectively constant concentration is produced by treating the entire surface of the emitter zone and using a small area central ohmic contact 9 (Fig. 2), several such contacts, or an annular contact. Another way of obtaining constancy of the minority carrier concentration in the emitter and hence of increasing its efficiency is to form the zone in two parts as shown in Fig. 3. The P-type part 2, which has a lower net impurity concentration than base zone 3 or P+ emitter part 6, is less than a diffusion length thick. Contact 4a to the emitter zone may be made in any of the ways mentioned above. An additional ohmic contact or contacts may also be provided to part 2 of the emitter zone. In operation, contact 4a or the additional contact(s) may be left floating or both connected in circuit.