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A Fluorine Cap for Be Outdiffusion in GaAs

IP.com Disclosure Number: IPCOM000108183D
Original Publication Date: 1992-Apr-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 1 page(s) / 53K

Publishing Venue

IBM

Related People

Baratte, H: AUTHOR [+3]

Abstract

Ion implantation of group II elements, such as Be or Mg, is used to produce p-type regions in GaAs. For low energy, high dose p-implants uncontrolled out-diffusion of the implanted species to the surface occurs during subsequent furnace or rapid thermal annealing. For example, when Be is implanted at N 1x1015cm-2, more than 80% of the implanted dose outdiffuses to the surface during subsequent annealing at >N 800~C. Therefore, it is difficult to produce shallow p+ -regions in GaAs which are suitable for providing ohmic contacts with low contact resistance. Co-implantaion of F with Be has been shown to reduce the Be outdiffusion during subsequent annealing. Typically, the energy of F implants is so adjusted that the F and Be profiles match each other.

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A Fluorine Cap for Be Outdiffusion in GaAs

      Ion implantation of group II elements, such as Be or Mg, is
used to produce p-type regions in GaAs. For low energy, high dose
p-implants uncontrolled out-diffusion of the implanted species to the
surface occurs during subsequent furnace or rapid thermal annealing.
For example, when Be is implanted at <N 20 keV and with doses >N
1x1015cm-2, more than 80% of the implanted dose outdiffuses to the
surface during subsequent annealing at >N 800~C.  Therefore, it is
difficult to produce shallow p+ -regions in GaAs which are suitable
for providing ohmic contacts with low contact resistance.
Co-implantaion of F with Be has been shown to reduce the Be
outdiffusion during subsequent annealing.  Typically, the energy of F
implants is so adjusted that the F and Be profiles match each other.
Even in cases where F and Be profiles were spatially separated, the F
distribution encroached well into the Be-implanted region.
Microstructurally, annealing of Be/F co-implanted samples leads to
the formation of Be-F complexes, or BeF2 precipitates in the
implanted region. The Be consumed in the formation of the complexes
or the precipitates is not electrically active.  This can
substantially reduce the electrical activation of the Be.
Furthermore, the presence of Be-F-related defect structures reduces
the mobility of the carriers in the implanted region.

      In this disclosure, the formation of an extremely thin (a few
mono-layers) F-ri...