| 摘要 |
1286753 Epitaxial growth SHARP KK 22 June 1970 [20 June 1969 (2)] 30220/70 Heading BIS [Also in Divisions H1 and C4] The conductivity-type imparted to a liquidphase-epitaxially grown semiconductor material by an amphoteric dopant included in the malt from which the material is grown is determined by the rate at which the malt is allowed to cool. The invention is based upon the discovery that the transition temperature at which the deposited material becomes p type (low crystallisation temperature range) rather than n type (higher crystallisation temperature range) decreases as the cooling rate of the malt increases. Thus in Fig. 3 curve A shows a cooling programme whereby firstly a p type layer and subsequently an n type layer are deposited on a substrate, while for curve B the converse is true. The substrate may be of p, n or i type material. Multi-layer structures (e.g. up to 13 layers of alternating conductivity types) may be formed by successively increasing and decreasing the cooling rate of the malt. A particular example comprises a pn pn light emitting GaAs diode in which the amphoteric dopant is Si, and if the cooling programme is modified to omit the upper p type deposition an npn GaAs transistor may be formed. The malt in these cases comprises Ga containing As and Si. A light emitting diode having only a single pn junction may be manufactured using the programme shown in Fig. 8(B), in which first n type and then p type GaAs is grown by liquid phase epitaxy on an n type GaAs wafer. In this case the temperature is initially raised very slowly after the malt covers the wafer, then very rapid cooling takes place at a rate sufficient to ensure that only n type material precipitates. The cooling rate is then reduced and held constant as firstly n type material and subsequently, when the malt temperature falls below the transition temperature, p type material, are deposited. Alternative semiconductor materials are GaP, InP, GaSb, GaN, AlSb, (GaAl)As, Ga(AsP) or (GaAl)P. Ge and Sn are referred to as alternative amphoteric dopants. |
