Electrooptical Devices

The current objectives of the electrooptical device program are: (1) to perform life tests on GaIn AsP/InP double-heterostructure (DH) diode lasers operating in the 1.0- to 1.2-micrometer wavelength region and analyze the degradation mechanisms, and (2) to fabricate and study avalanche photodiodes of similar composition GaInAsP operating in the same wavelength region. In the diode laser part of the program, 11 DH GaInAsP/InP lasers, operating continuously at room temperature, have been placed on life test. The first three devices, fabricated from one wafer, have logged over 4000, 3600, and 3200 hours, respectively, without degradation, and are still in operation. The eight devices fabricated from two additional wafers also show no evidence of internal degradation. However, a laser end-face contamination problem is present in several of the newer devices. Although this contamination can be removed from most of the devices by simple cleaning, improved fabrication procedures are currently being developed to eliminate the sources of the contamination. The p-n junction location in DH GaInAsP/InP diode lasers has been determined by use of a scanning electron microscope. Even though undoped or Sn-doped quaternary layers are n-type if grown on insulating substrates, the quaternary layers in the lasers are p-type, presumably due to Zn diffusion from the Zn-doped InP capping layer. As part of the avalanche photodiode program, proton bombardment and ion implantation in InP have been investigated for use in diode fabrication.