Thermal stability of the electrical isolation in n-type gallium arsenide layers irradiated with H, He, and B ions

Abstract

The stability of the electrical isolation in n-type GaAs layers irradiated with ions of different mass is compared. The irradiations were performed with proper doses of 1 H ϩ , 4 He ϩ , or 11 B ϩ ions to create specific damage concentration level which lead to: ͑i͒ the trapping of practically all the carriers ͑R s Ϸ10 8 ⍀/ᮀ), ͑ii͒ the onset of hopping conduction ͑R s Ϸ10 8 ⍀/ᮀ), and ͑iii͒ a significant hopping conduction ͑R s Ϸ10 6 ⍀/ᮀ). Irrespectively of the ion mass, the temperature range for which the isolation is preserved, i.e., R s Ͼ10 8 ⍀/ᮀ, extends up to 200 or Ϸ 600°C, respectively, for the cases ͑i͒ and ͑ii͒. In case ͑iii͒, this range comprises temperatures from Ϸ 400 to 650°C. Annealing stages at 200 and 400°C recover in a great extent the conductivity and improve the carrier mobility in low dose irradiated samples ͓case ͑i͔͒. In samples irradiated to higher doses ͓cases ͑ii͒ and ͑iii͔͒, the conductivity recovers in a single stage.

Electrical isolation of p-type GaAs layers by ion irradiation

“…During the dose accumulation from 1 ϫ10 10 cm Ϫ2 up to 1ϫ10 14 cm Ϫ2 there is a progressive increase of R s in consequence of carrier trapping and mobility degradation. 3,5 The dose for which R s just reaches its maximum value (Ϸ2ϫ10 9 ⍀/ᮀ) corresponds to D th . This maximum value of R s is established by the electrical conduction through the underneath SI GaAs substrate.…”

“…5 Specific doses and energies were chosen for these ions in order to produce approximately similar damage depth profiles. It was verified that the thermal stability of the isolation depends primarily on the concentration of the irradiation damage and only slightly on the ion mass.…”

“…For a fixed dose a higher stability of the isolation occurs in samples having a lower original carrier concentration. 5,6 Fewer investigations have been published regarding the electrical isolation of p-type GaAs by ion irradiation. 7,8 It was verified that the isolation of n-type and p-type GaAs layers of similar original sheet carrier concentration is attained after implantation of almost identical threshold doses of H or He ions.…”

Characterization of deep level traps responsible for isolation of proton implanted GaAs

“…The stability of the isolation during postirradiation thermal annealing increases progressively with the increase of the implanted dose and for a constant dose a higher stability of the isolation occurs in samples having the lower original sheet carrier concentration. 8 Isolation of n-type and p-type GaAs layers of similar original sheet carrier concentration is attained after implantation of identical ion doses. 9 This result was explained assuming that conduction electrons and holes are trapped by acceptor and donor centers, these centers being related to Ga and As antisite complex defects, respectively.…”

Electrical isolation of AlxGa1−xAs by ion irradiation

“…During dose accumulation R s increases as a consequence of carrier trapping and mobility degradation. 11 The dose for which R s reaches the maximum value (Ϸ5ϫ10 9 ⍀/sq) is hereafter called the threshold dose for isolation D th . A similar sharp increase in R s has been observed in all the samples, but the dose interval where it occurs shifts to higher doses proportionally with the initial free hole concentration p. It is interesting to mention that D th depends linearly on the free carrier concentration but does not depend on the aluminum content of the samples.…”