Kouichi Murakami

Dynamic behavior of pulsed-laser annealing in ion-implanted silicon: Measurement of the time dependent optical reflectance

Abstract In order to investigate the dynamic behavior of laser annealing processes, we have measured the time-dependent optical reflectance of ion-implanted silicon under pulsed-laser irradiation. We found that the amorphous to crystalline transition is completed within several hundred ns, depending on the laser energy and the pulse width.

Laser‐irradiation effects on unencapsulated GaAs studied by capacitance spectroscopy

The effect of Q‐switched ruby‐laser irradiation on unencapsulated unimplanted bulk GaAs has been investigated by means of deep‐level transient spectroscopy (DLTS) and C‐V carrier profiling. It was found that the concentration of a deep‐level center (Ec−0.83 eV) assigned to the A center decreases considerably as a result of laser irradiation, and that no deep levels (electron traps) more than 3×1013/cm3 are induced by the laser irradiation on the uncapped surface at a power level suitable for the recrystallization of an amorphous layer produced by ion implantation. No significant change in the free‐carrier profile at a depth deeper than 1500 A from the surface was observed after the laser irradiation.

Laser annealing of ohmic contacts on GaAs

Backside irradiation through the substrate with a Q‐switched Nd:glass laser (l = 1.06 mm) has been used to produce Au‐Ge ohmic contacts on GaAs. Conventional thermal alloying was done for comparison. The structure of the contacts was investigated by 2‐MeV He‐ion Rutherford backscattering technique, photographs, and I‐V characteristic measurements. The irradiated Au‐Ge contacts exhibit good ohmic contact behavior and good surface morphology. Ohmic contacts with specific contact resistance rc less than 2×10−5 W cm2 have been measured within the laser energy density of 0.3–0.5 J/cm2, while the thermally alloyed contacts yielded rc = 1.3×10−4 W cm2.

Effects of ion‐implanted atoms upon conduction electron spin resonance (CESR) in a Si : P system

The behavior of the conduction electron spin resonance of ion‐implanted (Si : P)  : Sb and (Si : P)  : Te systems is observed to be strongly modified by the presence of Sb or Te substitutional atoms in shallower surface layers; i.e., the ESR signal shows an anomalous line broadening. The origin of the anomalous broadening may be due to the spin‐orbit interaction between the conduction electrons contained within a thin layer (⩽25 μm) and implanted Sb or Te impurities contained within a thin layer (.=.0.1 μm).

Dynamic behavior of mode-locked Nd : YAG laser annealing in ion-implanted Si, GaAs, and GaP

By measuring the time‐dependent optical reflectivity, we have investigated the dynamic behavior of annealing with the 30‐psec pulse train of a mode‐locked Nd : YAG laser. It was first observed that at narrow ranges of high laser energy density, the reflectivity of implanted Si and GaAs increases slowly to the level consistent with liquid ones, except GaP, and remains at that level for a period less than 200 nsec. As to Si, the mode‐locked laser is confirmed to have a weak effect on temperature rise and, therefore, to produce a thin molten layer compared to Q‐switched Nd : YAG lasers.

Influence of spin density in implanted Si layers on pulsed‐laser annealing

In order to clarify an influence of the spin density or the optical absorption coefficient on the pulsed‐laser annealing effect, we have performed systematically ion‐backscattering and channeling analysis and ESR measurement as a funcion of spin densities in ion‐implanted Si samples. It was found that the spin density can yield a good criterion for predicting the annealing effect because the spin density is strongly correlated with the optical absorption coefficient. From spin‐density measurements, the initial absorption coefficient of the as‐implanted Si layer was found to be a very important factor which dominates the effect of laser annealing even if there is a nonlinear absorption mechanism.

Electron spin resonance of ion-implanted Si:P systems

Abstract The ESR of Si:P and (Si:P):Sb systems made by ion implantation has been observed. An anomalous line-broadening appears in the (Si:P):Sb system, and is considered to be due to the large spin-orbit interaction of Sb donor impurity. The effective spin-lattice relaxation time, T 1 eff , of both the systems is found to be dominated by a thin layer with the shortest relaxation time T 1 ( χ ).

Optical Absorption Measurements of α-Hydronaphthyl Radical Produced in Naphthalene by Electron Beam Irradiation and Hydrogen Atom Bombardment

Abstract The optical absorption was measured of a naphthalene single crystal irradiated with electron beam and of naphthalene powder bombarded with hydrogen atom, both at room temperature. The optical bands at 380 mμ and 540 mμ observed for both samples, were attributed to α-hydronaphthyl radical by the comparison of annealing behaviors of optical absorption bands with that of the ESR signal of this radical.

Deep levels in implanted, pulse-laser-annealed GaAs

Abstract Defects in proton implanted, pulse-laser-annealed GaAs have been investigated using capacitance spectroscopic techniques. Two defect centers similar to those induced by electron irradiation were observed by the proton implantation. The laser-annealing effect was studied as a function of the proton dose, and it was found that a significant annealing effect occurs for a low dose (≈10 12 cm −2 ) but that most of the defects remain for a high dose (≈10 14 cm −2 ) after the laser annealing at an energy density high enough to melt the damaged layer.

LASER ANNEALING EFFECTS IN ION-IMPLANTED GaAs

A Q-switched pulse laser-annealing effect in ion-implanted GaAs has been investigated by means of a He ion Rutherford backscattering technique, CV profiling, a deep level transient spectroscopy, and Hall effect measurements, in order to reveal the reason why no activity has been achieved for low dose implantation. A high activity similar to that obtained for implantations at a dose of 1×10 15 /cm 2 was obtained for samples implanted with 200 keV Si at a dose of 1×10 13 after implantation with 200 keV Si at a dose of 1×10 15 and an annealing at 850°C for 20 min. This suggests that formation of an amorphous layer is not necessary to obtain high doping efficiency. The effect of irradiation temperature and irradiation induced defect are also investigated.