| 摘要 |
1332942 Semi-conductor devices WESTERN ELECTRIC CO Inc 19 April 1971 [14 April 1970] 26731/71 Heading H1K First, second and third epitaxial layers are grown on a seed of a III-V compound material by successively applying a first solution comprising a first and a second group III element in which the III-V compound is dissolved, a second solution comprising the first group III element in the III-V compound is dissolved, and a third solution comprising the first and second group III elements in which the III-V compound is dissolved, the first and third epitaxial layers having wide band gaps and the second epitaxial layer having narrow band gaps. If the second solution also contains the second group III element it must be in a smaller concentration than in the first and third solutions. As shown, Fig. 1A, a seed crystal 19 of GaAs is mounted in a boat 14 within which is placed a solution holder 15 having recesses 16a, 16b, 16c containing solutions I, II and III respectively. The boat is provided with stops (25), 26 at opposite corners so that by appropriate tipping at predetermined temperatures in a cooling cycle each solution in turn is brought over the seed crystal. The floor of the boat 14 is provided with grooves 18 which remove scum from the solutions when the holder is moved relative to the boat. The furnace is supported by a cradle 22 which has a viewing port 23 located above the seed crystal and this provides a temperature gradient in the solution such that the free surface is cooler than the surface from which the epitaxial layer is grown. This ensures that the solution precipitates to a greater degree on floating nuclei at the free surface to enable very thin layers to be grown on the seed. A thermocouple 21 is used to measure the temperature of the seed. Solution I comprises an excess of GaAs dissolved in Ga and Al and doped with Sn, Si, Te, the deposited layer being of N type having a wide band gap. Solution II comprises an excess of GaAs dissolved in Ga and doped with Si or Si and Zn preferably compensated, the deposited layer being of P-type GaAs having a narrow band gap. Solution III comprises an excess of GaAs dissolved in Ga and Al and doped with Zn, the deposited layer being of P-type Ga 1-y Al y As having a wide band gap. The resultant device may be utilized as a junction laser or as an optical waveguide. In an alternative apparatus, Fig. 3 (not shown), the solution holder has provision for four solutions and is moved over the seed crystal by means of a push rod. The viewing port is omitted and the temperature gradient in the solutions is obtained by an auxiliary heater positioned below the crystal support. The apparatus may be subjected to mechanical vibration during deposition. The fourth solution is utilized to deposit a layer of GaAs doped with Zn or Ge to facilitate the provision of ohmic contacts which may be produced by evaporation of Cr and Au. The resulting slices may be cut and cleaved to produce laser diodes. |
