M.J. Harlow

Anomalous behaviour of dopants in atmospheric pressure MOVPE of InP

The doping level of p-type InP doped with Zn or Cd, incorporated into various structures, has been investigated as a function of the gaseous ambient to which the structure is exposed during cooling from typical MOVPE growth temperatures. It is found that the doping level is strongly dependent on this ambient. If AsH3 is present the doping level is lower by up to an order of magnitude than if PH3 is used, which in turn gives a doping level lower by up to a factor of two than H2 alone. Both MOVPE grown epilayers and Czochralski grown bulk crystals have been studied and found to behave similarly. SIMS experiments show that this is due to electrical deactivation rather than loss of the dopant species itself. n-Type InP and n- or p-type GaAs do not appear to be affected. Significant quantities of atomic H are found in samples exposed to the hydrides during cooling, consistent with their pyrolysis being catalysed by the semiconductor surface. The anomalous doping level phenomena are discussed in terms of a model involving deactivation of the dopant by complex formation with H, as observed by Johnson et al. in GaAs exposed to a hydrogen plasma.

1.5 /spl mu/m InGaAsP/InP large mode size laser for high coupling efficiency to cleaved single mode fibre

Increased mode size MQW BH lasers utilising a tapered active region and passive guide have shown cleaved fibre coupling losses down to 4.1 dB with threshold currents of 4.9 mA and 15 mA at 20/spl deg/C and 80/spl deg/C respectively.