GB1385634A - Gaa1as lasers - Google Patents

Abstract

1385634 Electroluminescence STANDARD TELEPHONES & CABLES Ltd 21 Aug 1973 39439/73 Heading C4S [Also in Division H1] A heterostructure GaAPAs semi-conductor laser has one limit of an optical confinement region including a P-N junction clearly defined at the boundary between layers 11 and 12 by an abrupt increase in aluminium concentration in layer 12, while the other limit of the confinement region is less precisely established by arranging the aluminium concentration in layer 11 to increase without discontinuity from its boundary with layer 12 to its boundary with a substrate 10. The layers 10, 11 and 12 respectively comprise GaAs, Ga (1-x) Al x As and where y>x, y is constant and x decreases progressively in the direction from the substrate 10 to layer 12. A further layer 13 of GaAs on layer 12 facilitates the provision of a metallized contact. In Fig. 1 the substrate 10 and layer 11 are N-type and the layers 12, 13 are P-type, the zinc doping of layer 12 being diffused into layer 11 to produce a P-N junction 11a. The reduction in concentration of aluminium through layer 11 is produced by progressively deleting the aluminium content in a melt during the growth process, concentration values being given. The resulting variation of refractive index n through the layers which delineates the confinement region is shown in Fig. 2. In alternative germanium doped structures, Figs. 3 and 5 (not shown), the substrate may be N- type or P-type with a corresponding doping relationship through the layers, the P-N function being defined by the boundary between layers 11 and 12.