Abstract: The apparent differential output power or quantum efficiency of a semiconductor laser, such as a double heterostructure laser diode, is reduced by means of a circuit which shunts the laser and includes a threshold device. The I-V characteristic of the shunt circuit intersects that of the laser at V.sub.x such that at voltages below V.sub.x the current through the laser exceeds that through the shunt, and conversely above V.sub.x. Specific embodiments of the shunt circuit include a resistor in series with either a zener diode or one or more forward-biased conventional diodes.

Abstract: Current confinement in semiconductor devices by means of buried high resistivity zones is described. For example, in a stripe geometry, semiconductor, junction laser the laterally separate, high resistivity zones, which confine current flow in a narrow channel between the upper and lower electrical contacts, are buried below the upper contact. This configuration permits current to flow from the upper contact into the body of the semiconductor over greatly increased area before it enters the channel. The current density at the interface between the upper contact and the semiconductor body is thereby reduced, making the quality of that interface less important. Several processes which employ proton bombardment for fabricating the laser are also described: (1) in one the normal sequence of Zn diffusion and proton bombardment is reversed, and (2) in the other the profiles of Zn doping and proton damage are suitably tailored.