K. V. Vaidyanathan

Electrical profiling and optical activation studies of Be‐implanted GaAs

Differential resistivity and Hall‐effect measurements have been utilized to study the annealing behavior and electrical carrier‐distribution profiles of Be‐implanted GaAs. A maximum of 90–100% electrical activation occurs during 900 °C anneals for implanted Be concentrations less than ∼5×1018 cm−3. For higher fluences, however, a heavily concentration‐dependent diffusion is observed, and the measured electrical activation is complicated by outdiffusion of Be into the Si3N4 encapsulant. In these cases, a maximum in the electrical activation appears for annealing near 700 °C. Low‐temperature (5 °K) photoluminescence substantiates previous findings that 900 °C annealing results in maximum optical activation and lattice recovery.

R.F. plasma deposition of silicon nitride layers

Abstract A versatile r.f. plasma deposition system used to deposit high quality Si3N4 films at low temperature (200–350°C) is described. By introducing the reactant gases separately and reactively reducing the oxygen content of the system, films which exhibited very little oxygen contamination could be deposited. Rutherford backscaterring studies were used to evaluate the atomic composition of the films. The composition was related to other parameters such as the index of refraction, the etch rate and the deposition rate. The nitride layers described here were used successfully to anneal ion-implanted GaAs with negligible surface degradation.

Annealing studies of Be‐doped GaAs grown by molecular beam epitaxy

Differential resistivity and Hall effect measurements and secondary ion mass spectrometry (SIMS) are used to study the annealing behavior of GaAs doped with high Be concentrations during growth by molecular beam epitaxy (MBE). The diffusion coefficient of MBE‐grown Be in GaAs is determined to be (0.5–1) ×10−13 cm2/sec at 900 °C, a value which is two orders of magnitude lower than that for implanted Be of equal concentration [(2–3) ×1019 cm−3]. The concentration dependence of the diffusion of MBE‐grown Be in GaAs is also observed to be substantially less than that for implanted Be. The implantation of He in Be‐doped MBE layers to create lattice damage does not significantly affect the Be diffusion in a subsequent anneal.

Diffusion studies of Be-implanted GaAs by SIMS and electrical profiling☆

Abstract Secondary ion mass spectrometry (SIMS) has been used with differential resistivity and Hall effect measurements to study the 900°C diffusion of implanted Be in GaAs. Some outdiffusion of Be into the Si3N4 encapsulant occurs for surface Be concentrations above 1 × 1018 cm−3. However, excellent agreement between the electrical and atomic profiles indicates that 85–100% of the Be remaining after annealing is electrically active. The concentration-dependent diffusion observed for implanted Be in GaAs was not significantly altered in experiments using hot substrate implants, two-step anneals, or annealing with Ga and As overpressure.

Photoluminescence study of native defects in annealed GaAs

Abstract Low temperature (6°K) photoluminescence measurements have been performed on GaAs annealed under various conditions, to study defects generated by outdiffusion of the constituent atoms. Several defect-related luminescence peaks have been observed and associated with Ga and As outdiffusion. The outdiffusion of these elements during annealing to 850°C in vacuum and with Ga or As overpressure and SiO 2 coatings is studied by monitoring the intensities of these peaks.

Photoluminescence from Be‐implanted GaAs

Low‐temperature (6 °K) photoluminescence data on Be‐implanted GaAs are presented. A luminescence band centered at 1.4902 eV is related to recombination involving the Be acceptor. Annealing to 900 °C with Si3N4 encapsulation is shown to optically activate the implanted Be and reorder the lattice. The ionization energy of Be is estimated to be 22±3 meV.

Temperature dependence of photoluminescence from Be‐implanted GaAs

Photoluminescence data from Be‐implanted GaAs are presented for the temperature range 3–120 °K. A luminescence band at 1.493 eV is associated with recombination from the conduction band to neutral Be acceptors, based on the temperature dependence. The binding energy of Be acceptors in GaAs is estimated to be 28.4 meV from the temperature dependence of the peak energy of this band.

Comment on ’’Evidence for electronic stopping in ion implantation: Shallower profile of lighter isotope 10B in Si’’

A recent paper bases several conclusions regarding electronic and nuclear stopping powers of silicon for implanted boron on a few capacitance‐voltage measurements of impurity profiles. We suggest here that the accuracy of C‐V data is insufficient to distinguish small changes in projected range, and that measurements with better resolution are required.

Annealing studies of Be-implanted GaAs0.6P0.4

Differential resistivity and Hall effect measurements and secondary ion mass spectrometry (SIMS) are used to study the annealing behavior of Be-implanted GaAs0.6P0.4. Results similar to that previously reported for Be-implanted GaAs are observed, including outdiffusion of Be into the Si3N4 encapsulant during 900‡C annealing of high dose implants. Nearly all (85–100%) of the Be remaining after a 900‡C, 1/2 hr anneal is electrically active. However, the electrical activation at low annealing temperatures (600–700‡C) is much lower in GaAs0.6P0.4 than in GaAs. A substantial amount of diffusion is observed even for the low fluence Be implants in GaAs0.6P0.4 annealed at 900‡C, indicating a greater dependence of the diffusion on defect-related effects in the ternary.

Impurity Distribution of Ion-Implanted Be in GaAs by Sims, Photoluminescence, and Electrical Profiling

Atomic, optically active, and electrically active profiles measured for 250 keV ion-implanted Be in GaAs as a function of fluence have been correlated. Be atomic depth profiles were obtained by secondary-ion mass-spectroscopy (SIMS) techniques. Photoluminescence and Hall effect measurements made in conjunction with successive layer removal were used to obtain the optically and electrically active profiles. Atomic SIMS profiles obtained from samples implanted to a fluence of 6X10113cm-2 showed no major distribution changes after a 900°C, 30 min anneal treatment. Electrically active profiles obtained from duplicate samples had distributions which were similar to the SIMS results. Hall effect and resistivity measurements after annealing indicated nearly complete electrical activity of the implanted Be, with mobility values typical of p-type bulk material.