Experimental study of the hydrogen complexes in indium phosphide

Abstract

The structure of the H-related complexes in p-type InP and in liquid encapsulated Czochralski semiinsulating InP:Fe has been studied from the vibrational absorption of their PH stretching modes. The acceptor complexes are produced by plasma hydrogenation so that PD modes have been investigated also. The study has first been performed at 6 K on the fundamentals and on the most intense of the first overtones. The trends in the frequencies and widths of the PH modes of the H-acceptor complexes for Be, Zn, and Cd acceptors are discussed and explained qualitatively. In InP:Fe, the PH intrinsic modes are sharper than those of the acceptor complexes indicating a weaker interaction with the environment. This study has been followed by the measurement of the temperature dependence of the frequencies and of the linewidths for increasing temperatures. The frequency shifts and the broadenings of the lines are interpreted by the temperature-dependent random dephasing of the vibration of the high-frequency oscillators in the excited state. The analysis shows that the PH mode in the acceptor complexes couples to TA phonons of the InP lattice while the one in the complexes involving a vacancy couples to a two TA phonon combination. The anharmonicity of the P-H bonds is comparable to the one in phosphine. A comparison of the anharmonicity parameters derived from the overtone measurements with those derived from the hydrogen isotope effects gives evidence of the interaction between the H atom and the lattice. The amplitude of vibration of the D atom is smaller than that of the H atom and this explains why the interaction of the D atom with the lattice is smaller. This is the reason why the width of the PD modes is smaller than that of the corresponding PH modes. The splitting of some of the PH lines in samples subjected to a uniaxial stress has been studied. The splitting of the PH;Zn mode is in full agreement with a P-H bond along a (111)axis. The same (111)orientation of the P-H bond is also found from the splitting of a line attributed to an In vacancy "decorated" by a H atom ( VI"(PH)). The splitting of the strongest line in InP:Fe leads to its attribution to a PH mode in a cubic center containing four H atoms ( V&"(PH)4). The presence of this center seems to account for most of the hydrogen present in InP:Fe. Upon annealing of the InP:Fe samples, V&"(PH)4 is a source of atomic hydrogen that can be trapped by other defects and it can leave partially hydrogenated In vacancies.

Spectroscopy of Proton Implanted GaN

“…The annealing behavior of the defects we have observed in H-implanted GaN is similar to that of defects seen previously in H-containing InP. In as-grown [13][14][15] and H-implanted 16 InP there is a strong band at 2316 cm -1 that has been assigned to a P-H stretching mode of a V In -H 4 complex. 14,15,17 A lower frequency band at 2201 cm -1 has also been assigned to a P-H stretching mode of V In -H. 14,17,18 Additional weak lines have been seen between these frequencies.…”

“…In as-grown [13][14][15] and H-implanted 16 InP there is a strong band at 2316 cm -1 that has been assigned to a P-H stretching mode of a V In -H 4 complex. 14,15,17 A lower frequency band at 2201 cm -1 has also been assigned to a P-H stretching mode of V In -H. 14,17,18 Additional weak lines have been seen between these frequencies. 14, 16 Ewels et al 17 have calculated the frequencies of the V In -H n complexes and have proposed that the partial dissociation of the V In -H 4 complex upon annealing leads to the formation of V In -H n centers with fewer H atoms, and thus lower frequencies, to explain the presence of several Hstretching bands.…”

“…In a previous study of H and D implanted InP, similar results were obtained and no line splittings were observed, 16 even though the line observed at 2316 cm -1 has been assigned to a V In -H 4 complex. 14,15,17 It was found later that in samples where H and D had been introduced during growth (which gives rise to much sharper lines), the 2316 cm -1 band was split into a triplet by the presence of both H and D, but with a line splitting of only ~ 0.5 cm -1 , too small to have been observed in the implanted samples. 15 The line widths in our proton implanted GaN samples arẽ 5 cm -1 which would also prevent the observation of such small line splittings.…”

Vacancy- and acceptor-H complexes in InP

“…Uniaxial stress measurements show the centre to have T d symmetry [4], consistently with V In H 4 . The LVM lies close to that of other P-H-related modes, and this is consistent with results obtained for VH 4 in Si [5]. The defect can be created by proton irradiation [6], which also leads to the creation of the required In vacancies.…”

“…The most intense H-related mode in as-grown crystals occurs at 2316 cm −1 (found in InP:Fe as well as in crystals without Fe), and has been associated with V In H 4 [4].…”