Co-implantation of Al+, P+, and S+ with Si+ implants into In0.53Ga0.47As

Abstract

Elevated temperature, nonamorphizing implants of Si þ , and a second co-implant of either Al þ , P þ , or S þ at varying doses were performed into In 0.53 Ga 0.47 As to observe the effect that individual co-implant species had on the activation and diffusion of Si doping after postimplantation annealing. It was found that Al, P, and S co-implantation all resulted in a common activation limit of 1.7 Â 10 19 cm À3 for annealing treatments that resulted in Si profile motion. This is the same activation level observed for Si þ implants alone. The results of this work indicate that co-implantation of group V or VI species is an ineffective means for increasing donor activation of n-type dopants above 1.7 Â 10 19 cm À3 in InGaAs. The S þ co-implants did not show an additive effect in the total doping despite exhibiting significant activation when implanted alone. The observed n-type active carrier concentration limits appear to be the result of a crystalline thermodynamic limit rather than dopant specific limits. V

N-type Doping Strategies for InGaAs

“…Overall most co-implant studies lead to modest or inconsistent deviations in activation from silicon-only implant cases, and were primarily measured from Hall Effect techniques or sheet numbers [49][50][51][52][53]. Furthermore dopants co-implanted with Si in InGaAs did not result in active carrier concentrations as high as the sum of their individual electrical solubility limits [54].…”

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

“…Si shows heavily concentration dependent diffusion but there is limited theoretical prediction that Si As donors or inactive Si Ga -Si As next-nearest neighbor neutral pair configurations are mobile in GaAs 76,82 despite experimental evidence indicating that heavily compensated Si is highly mobile and inactive in InGaAs. 72 The plots of Si diffusion in Fig. 3 are indicative of heavily concentration dependent diffusion where Si concentrations above 3 × 10 19 cm −3 is highly mobile.…”

“…Previous reports indicate that Si and Se have nearly the same maximum electrically active carrier concentration in InGaAs 50 and this result seems remarkably coincidental if the two species are compensated via entirely different mechanisms (amphoteric and chemical solubility limited respectively). Vacancy-dopant complexing better explains the species independent and non-additive doping of multiple species 56,72,73,92 in InGaAs and GaAs since vacancy creation and subsequent compensation of donors depends primarily on the Fermi level of the material.…”

“…28 Damage arguments for limited dopant activation from implantation lack convincing evidence and more recent result suggest that the thermal treatments used to activate dopants in ion implanted substrates result in the formation of compensating defects. 53,72 Previous studies have indicated that high doping levels of Si and Se in MBE grown InGaAs substrates are metastable. In particular, Watanabe et al observed that at annealing temperatures below 700…”

“…Generally, the reported improvements in electrical activation from co-implantation of a group III or group V dopant with a group IV dopant is much less than the co-implant dose 49,58,[64][65][66][67][68][69][70] and some studies indicate that there is no improvement in activation from co-implantation. 71,72 Without direct measurement of Si sublattice occupation it is impossible to say that co-implantation is completely ineffective at modulating the degree of amphoteric behavior of a group IV dopant but there appears to be limited practical improvement in electrical activation. Dual implant studies of group IV and group VI species or multiple group IV dopants suggest that the total activation of dopants in InGaAs and GaAs is not the sum of the individual electrical solubility of the group IV dopants and the group VI dopants.…”