GB1065459A - Improvements in and relating to semiconductor junction lasers - Google Patents

Abstract

1,065,459. Semi-conductor laser devices. MULLARD Ltd. Dec. 18, 1963, No. 49999/63. Headings H1C and H1K. A semi-conductor junction laser is positioned between two electrically conductive heat sinks each having two plane parallel surfaces coplanar with the two polished parallel surfaces of the laser. As shown in Fig. 1, a semi-conductor 1 having a PN junction 4 is mounted between conductive heat sinks 2, 3. The accurately polished plane parallel surfaces 7, 8 perpendicular to the plane of the junction 4 and forming the laser resonant cavity are made coplanar with plane parallel front surfaces 9, 10 of the heat sinks 2, 3 and rear surfaces. Ohmic contacts are applied to the semi-conductor body and layers of solder are interposed between these contacts and the respective heat sinks, Fig. 2. During the manufacture of the laser the coplanar surfaces are formed by the simultaneous grinding of the semi-conductor body and the heat sink members. A reflective coating may be applied to one of the surfaces 7, 8 in the vicinity of the PN junction. In operation, the laser is placed in liquid nitrogen and the current applied to electrical leads soldered to sinks 2, 3 is pulsed. An electrically conductive expansion member may be mounted between one heat sink and the respective adjacent region of the semi-conductor body in order to compensate for differences in expansion coefficients of body 1 and heat sinks 2, 3. The body 1 may be N-type tellurium doped gallium arsenide having a P- type region formed by diffusion of zinc. Manufacture of device.-A slice of N-type gallium arsenide 6 doped with tellurium has zinc diffused into its surface to form a PN junction 4. After grinding and etching to produce a wafer of the correct area and thickness an ohmic contact 14 is made to P-type region 5 alloying a pellet of an alloy of bismuth and silver and an ohmic contact 15 is made to N- type region 6 by alloying a pellet of an alloy of bismuth, tin and platinum. The wafer is then mounted to heat sinks 2, 3 by applying a thin layer of indium 16, 17 to the surfaces of the heat sink and soldering the wafer thereto. After potting the assembly the surfaces 7, 8 of the body 1 and the copolanar front and rear surfaces of sinks 2, 3 are formed by sawing off the resin and grinding to remove material simultaneously from the sinks and body 1.