Schottky contacts on reactive-ion etched InGaP

Abstract

We report on the technology and properties of Schottky contacts on reactive-ion etched n-In0.49Ga0.51P (n=7.5×1017 cm−3). A mixture of CH4/H2 was used for a controllable smooth dry etching of InGaP while a CCl2F2-based plasma was shown to enable a highly selective etching of GaAs over InGaP. Current–voltage (I–V), capacitance–voltage (C–V) methods and deep-level transient spectroscopy (DLTS) were used for diode characterization. CCl2F2-based reactive-ion etching (RIE) led to diodes with barrier heights of 0.67 eV (from I–V measurements) and ideality factors of 1.24, which are parameters that are very close to those of the reference (not dry etched) sample. Additional C–V and DLTS characterization has confirmed no detectable damage for CCl2F2-based RIE. On the other hand, hydrogenation after CH4/H2 plasma led to substantial passivation of donors which were successfully reactivated after 430–470 °C rapid thermal annealing (RTA). For this type of processing we measured barrier heights of 0.70–0.75 eV and ideality factors of 1.25–1.27, depending on the temperature of the RTA. DLTS on CH4/H2-RIE based diodes has shown that, in contrast to the reference sample, no bulk deep traps are generated with RTA. We point out that thermal treatment also led to changes in the interface states density which may be responsible for the diode barrier height increase.