Surface passivation techniques for InP and InGaAsP p-n junction structures

Surface passivation techniques developed for InP and InGaAsP avalanche photodiodes have resulted in reductions of dark current as large as four orders of magnitude, to values as low as 1.6 × 10
^-6
A/cm
²
at 0.9V
b
. Devices consisting entirely of InP have been passivated with plasma-deposited Si
3
N
4
, and those with a InGaAsP layer but with the p-n junction in InP have been passivated with polyimide. Neither of these techniques successfully reduces dark currents in devices with the p-n junction in the InGaAsP, but a film of photoresist sprayed with SF
6
as the propellant has given excellent results.