Electrical isolation of p-type GaAs layers by ion irradiation

Abstract

The electrical isolation of p-type GaAs layers doped with acceptor impurities incorporated in the Ga sublattice ͑Mg͒ or As sublattice ͑C͒ was studied using proton bombardment. It was found that practically the same proton dose is required to reach complete isolation ͑isolation threshold dose, D th ͒ in layers doped with either Mg or C of comparable original sheet hole concentration (p s ). This result is evidence that the sublattice where the acceptor dopant atoms are incorporated does not play any significant role for the isolation formation process in GaAs. The behavior of the recovery of the conductivity during subsequent thermal annealing was found very similar in Mg and C doped samples irradiated to equal proton doses. In samples irradiated to doses ϽD th , the sheet resistance (R s ) increases during annealing at temperatures Ͼ100°C, reaches a maximum at Х200°C, and then decreases progressively toward the original value. For proton doses ranging from D th to 5D th , the isolation is preserved up to the temperature of Ϸ500°C. The temperature of Ϸ700°C was found to be the upper limit for the thermal stability of the isolation in samples irradiated to doses of 100 D th .

Implant isolation of Zn-doped GaAs epilayers: Effects of ion species, doping concentration, and implantation temperature

“…The sheet resistance reaches a narrow plateau when the concentration of deep levels is of the same magnitude as the free hole concentration, and is determined by the sheet resistance of the underlying SI GaAs substrate. 1,2,[7][8][9][10]15,16 Any further increase in dose beyond this plateau results in the monotonic decrease in R s ͑closed circles͒ because of hopping conduction of holes between closely spaced defect potential wells. 18 Following Ref.…”

“…This is because the vacancies are precursors for the creation of antisite defects. The choice of the total number of replacements stems partially from the recent discussion of Boudinov et al 16 that the defect responsible for the isolation in p-type GaAs is the double-donor arsenic-antisite, As Ga , and the results discussed below. By including the data point for 0.1 MeV H ions in Fig.…”

“…14 -16 In some investigations the conductive p-type layers were formed in semiinsulating GaAs substrates by C or Mg ion implantation followed by annealing to activate the dopant atoms and to remove implantation-induced damage. 15,16 Since ion implan-tation produces a nonuniform doping profile, 15,16 and because practical devices are manufactured by epitaxial growth, it may be more reasonable to investigate implant isolation processes in uniformly doped p-type epilayers. 14 The results reported in Refs.…”

Modeling Electrochemical Etching of Proton Irradiated p-GaAs for the Design of MEMS Building Blocks

“…Going from the recoil stop to the eletric conductivity it must be taken into account that the resistivity increases strongly non-linearly with the defect distribution, as discussed before, thus giving a strongly non-linear dependence of etching rate and proton fluence. The experimental values of the correlation between defect concentration and resistivity measured by Boudinov et al [20] may be directly mapped to the values shown in Fig. 2 by taking into account the material's original resistivity and the proton fluence, thus yielding conductivity distributions as shown in Fig.…”

“…Many studies have been carried out in order to understand the nature of such defects leading to insulating GaAs and their influence on the electrical properties of irradiated GaAs substrates [8], [14], [16]- [19]. The decrease in conductivity, and in our particular electrochemical etching case the decrease in hole conduction, has been shown to be due to trapping of holes at specific trap centers [18], [20]. Such traps are created due to nuclear energy loss and it is thus obvious to relate the experimental defect production rate to the one calculated with e. g. SRIM [21], as shown in the past.…”