Self‐Compensation in Rapid Thermal Annealed Silicon‐Implanted Gallium Arsenide

Abstract

This paper describes the regrowth and activation characteristics of Si-implanted GaAs resulting from rapid thermal annealing (RTA) using optical radiation heating. Activation of Si in GaAs by RTA is observed to increase with temperature up to a maximum value, then decrease sharply for additional increases in temperature. The optimum annealing temperature is dependent on both implant dose and annealing time. This activation behavior in RTA time regimes is explained by the competition between kinetic and thermodynamic factors. From Arrhenius plots of the activation data, regrowth under these conditions is shown to be a thermally activated process. Electrical and photoluminescence measurements demonstrate that Si self-compensation limits activation at high annealing temperatures.Ion implantation has become the most viable method available for controllably and reproducibly introducing shallow conductive layers into GaAs for application to digital and monolithic microwave integrated circuit fabrication. A requisite step in ion implantation processing is a high temperature anneal to reduce the ion damage produced in the crystal during implantation and to activate the implanted dopant. Furnace annealing at about 850~ for 15-20 rain with the use of arsenic overpressure or encapsulating layers is normally employed for activating implants. Rapid thermal annealing (RTA) has been shown to yield higher peak carrier concentrations and sharper dopant profiles than furnace annealing (1). More importantly, RTA has greater application for annealing selfaligned n + implants in MESFET and HEMT devices and for implanted contact layer activation in other structures where long duration furnace anneals can cause degradation. Silicon has been studied here, as it is the most commonly employed n-type species for GaAs implantation. Because of the amphoteric nature of Si in GaAs, its activation behavior can be strongly dependent on the parameters of the annealing process. In this work, the regrowth and activation characteristics of Si-implanted GaAs and the carrier loss due to self-compensation under RTA conditions are studied and discussed.

Capless Rapid Thermal Annealing of GaAs Implanted with Si+ Using an Enhanced Overpressure Proximity Method

“…The activation efficiency for the GaAs proximity technique appears to saturate at a maximum activation of 12% after a 10s anneal. The requirement for higher anneal temperatures with increasing dose is consistent with previous RTA and furnace annealing studies of Si + implanted into GaAs (19,20). 3 and 4, however, these conditions exceed the allowable range for GaAs proximity anneals and therefore practical activations will be below 12%.…”

Review—Dopant Selection Considerations and Equilibrium Thermal Processing Limits for n+-In0.53Ga0.47As

“…It is generally assumed in literature that amphoteric dopants such as C, Si, Ge, and Sn are limited in activation due to the propensity to exist in both a donor and acceptor configuration and thereby cause self-compensation. [37][38][39][40][41][42][43] MBE experiments are perhaps the most convincing evidence that group IV dopants, and Si in particular, can be used as both a n and p-type dopants. [44][45][46][47][48] It is not clear if p-type doping in MBE growth from species which are nominally n-type via ion implantation or source diffusion remain p-type with subsequent thermal annealing.…”

Scaling Challenges for Advanced CMOS Devices

“…Group IV dopants are referred to as 'amphoteric'. It is assumed in literature that amphoteric dopants such as C, Si, Ge, and Sn are limited in activation due to their propensity to exist in both a donor and acceptor configurations, thereby causing selfcompensation 153,154 . Amphoteric compensation may be a downside to the use of group IV dopants in III-V materials, but implanted Si often shows similar or better activation than implanted group VI dopants such as Se when treated to equilibrium thermal processing 155 .…”