GB1170799A - Semiconductor devices - Google Patents

Abstract

1,170,799. Electroluminescence. INTERNATIONAL BUSINESS MACHINES CORP. 18 May, 1967 [15 July, 1966], No. 23009/67. Heading C4S. [Also in Division H1] An electroluminescent diode includes a compensated P-type region 12 containing an excess concentration of acceptor impurities of the order of 10<SP>17</SP> cm.<SP>-3</SP> or lower and a free hole concentration of less than 10<SP>17</SP> cm.<SP>-3</SP>, at which electrons injected across the forward-biased junction 16 recombine with holes trapped at the acceptor level causing the emission of radiation of lower energy (i.e. longer wavelength) than the material band gap. Owing to the low acceptor excess, emission takes place throughout the region 12, which may be 50-60 Á thick and which may or may not be provided with a P+ contact region 14 from which positive holes are injected into the region 12. In the preferred form the diode is of GaAs containing Si, Ge or Sn as a dopant. These elements are all amphoteric in GaAs, dependent on the precise mode of growth. A melt of GaAs containing Si and a small stoichiometric excess of Ga is contacted at 935‹ C. with a (100) surface of an N-type GaAs substrate containing Si as the dopant. The surface of the substrate melts, and, on cooling gradually, recrystallizes as GaAs including Si in both donor and acceptor forms. The initially recrystallized layer contains an excess of donors, and is thus N-type, but as the temperature is reduced the subsequently recrystallized portion contains a small excess of acceptors. The completed crystal is lapped to the required thickness of region 12, and Zn is diffused in at 650‹ C. to provide the P+ type region 14. If the region 14 is omitted, hole injection into the region 12 occurs directly from the ohmic contact 20. The completed device may be potted in an antireflecting coating of epoxy resin. The invention is also applicable to semi-conductor lasers.