Assessment of oxygen in gallium arsenide by infrared local vibrational mode spectroscopy

Abstract

Two infrared local vibrational mode (LVM) absorption lines occurring at 715 and 845 cm−1 shift to 679 and 802 cm−1 in gallium arsenide doped with 18O, proving that the lines arise from the vibrations of oxygen impurities. The 715 cm−1 line exhibits a triplet 69,71Ga isotope fine structure consistent with that expected from a quasi-substitional VAs-O center. The 845 cm−1 line appears as a closely spaced doublet expected for a bonded interstitial oxygen atom.

Microscopic structure of oxygen defects in gallium arsenide

“…2 In addition, LV frequencies are detected also at 731 and 715 cm Ϫ1 (A and B, respectively͒. 3 These frequencies show the characteristic triplet fine structures caused by the 69 Ga and 71 Ga isotopes, 3,4 and the 18 O→ 16 O isotopic shifts 2 leading to the unambiguous conclusion that the frequencies originate from a Ga-O-Ga structure. We call the defect containing this Ga-O-Ga structure simply the Ga-O-Ga defect.…”

“…14,15. Table I shows the calculated structures and LV frequencies for the three models O As , O I , and (As Ga ) 2 -O As , as well as the experimental LV frequencies for the Ga-O-Ga defect. 2,6 For reference, we note that our calculated value of 869 cm Ϫ1 for the asymmetric stretching LV frequency of the Ga-O-As defect agrees closely with the measured vibration frequency of 845 cm Ϫ1 , 2 the difference being a signature of the tendency of LDA for overbinding.…”

“…The as-grown GaAs crystal is semi-insulating and As-rich, containing about 10 16 EL2 defects/cm 3 , identified as As Ga antisites. 1,2 Oxygen in the puckered bond-center defect Ga-O-As gives rise to an experimentally detected local vibration ͑LV͒ frequency doublet at 845 cm Ϫ1 . 2 In addition, LV frequencies are detected also at 731 and 715 cm Ϫ1 (A and B, respectively͒.…”

“…1,2 Oxygen in the puckered bond-center defect Ga-O-As gives rise to an experimentally detected local vibration ͑LV͒ frequency doublet at 845 cm Ϫ1 . 2 In addition, LV frequencies are detected also at 731 and 715 cm Ϫ1 (A and B, respectively͒. 3 These frequencies show the characteristic triplet fine structures caused by the 69 Ga and 71 Ga isotopes, 3,4 and the 18 O→ 16 O isotopic shifts 2 leading to the unambiguous conclusion that the frequencies originate from a Ga-O-Ga structure.…”

“…This model is presented schematically in Fig. 1 and consists of two arsenic antisites (As Ga ) and one offcentered substitutional oxygen in arsenic vacancy ͓(As Ga ) 2 -O As ͔.…”