V. R. Deline

Physical and electrical properties of laser‐annealed ion‐implanted silicon

The use of a laser as a tool for annealing of ion‐implantation damage is described. The principal results obtained are as follows: (1) electrical measurements show that activity comparable to that of a 1000u2009°C 30‐min anneal can be obtained; (2) TEM measurements show that complete recrystallization of the damaged layer occurs during the laser anneal; (3) impurity profiles obtained from SIMS measurments show that the dopant atoms remain in the LSS profile during annealing. Simple diodes were fabricated to examine the feasibility of the method for device fabrication.

Mechanism of the SIMS matrix effect

Quantization of ion microprobe mass spectrometric analyses has been complicated by the variation in the ion yield of an element contained in different matrices. This work demonstrates that, for O− and Cs+ bombardment, these ion‐yield variations are solely attributable to variations in the matrix sputtering yield. It is argued that the matrix sputtering yield determines the near‐surface concentration of the ion‐yield‐enhancing species O and Cs.

A unified explanation for secondary ion yields

The pure element secondary ion yields under oxygen and cesium ion bombardment are shown to be solely dependent on a) the ionization potential (or electron affinity for negative ionization) of the sputtered atom and b) the reciprocal of the matrix sputtering yield which determines the equilibrium concentration of implanted oxygen or cesium. This unified approach accounts for the yields of C±, Si±, Ge± and Sn± from the pure elements as well as of Ga± and As± from gallium arsenide.

Redistribution of Cr during annealing of 80Se‐implanted GaAs

Cr in‐depth distributions have been measured in Se‐ion‐implanted GaAs as a function of postimplant annealing using secondary‐ion mass spectrometry (SIMS). Analysis shows that Cr redistributes into regions of residual damage following 800u2009°C annealing. As the damage anneals at higher temperatures, however, the Cr tends toward the GaAs surface. This phenomenon offers a plausible explanation of the discrepancies between the observed electrical and chemical distributions of ion‐implanted Se.

Use of a scanning cw Kr laser to obtain diffusion‐free annealing of B‐implanted silicon

The use of a continuous scanned Kr ion laser as a tool for annealing of boron‐implanted silicon is described. Conditions were found that produce high electrical activity and crystallinity of the implanted layer without redistribution of the boron from the as‐implanted profile.

Back surface gettering and Cr out‐diffusion in VPE GaAs layers

Mechanical back surface damage gettering has been investigated for improving the quality of GaAs substrates and VPE layers on semi‐insulating GaAs. It has been shown that the pregettering of substrates reduces the interfacial defect density and alters the level of Cr out‐diffusion into the VPE layer during growth. At a postdeposition anneal temperature of 800u2009°C, Cr out‐diffusion into the VPE layer is relatively suppressed in the pregettered substrate, while the ungettered sample shows larger concentrations of Cr within the epitaxial layer.

Ion‐implanted Se in GaAs

Electrical measurements are combined with the technique of secondary‐ion mass spectrometry (SIMS) in order to experimentally analyze and correlate the diffusion and activation of ion‐implanted selenium in GaAs. A theory is presented based on the assumption of four chemically different species of selenium: (1) substitutional selenium, (2) interstitial selenium, (3) selenium complexed with a gallium vacancy, and (4) precipitated selenium. It is proposed that the interaction between these four species dictates the resulting redistribution and electrical activation of ion‐implanted layers. The factors governing these interactions are investigated, and it is speculated that only substitutional selenium is a shallow donor. In addition, it is speculated that the species responsible for redistribution of impurity profiles is the selenium‐gallium vacancy complex. Precipitates and interstitial selenium appear to neither diffuse nor act like donors in GaAs. A model is developed which formalizes these observations in...

Incorporation of boron during the growth of GaAs single crystals

A study of GaAs prepared by conventional Bridgman techniques and by liquid‐encapsulated Czochralski methods reveals that only small amounts of boron are incorporated from the boric oxide encapsulant. When a pyrolytic boron nitride crucible is used, there is a 100‐fold increase in the amount of incorporated boron, suggesting some decomposition of the boron nitride.

Alloying of Au layers and redistribution of Cr in GaAs

Alloying of Au films on Cr‐doped GaAs substrates and Sn‐doped LPE layers grown on semi‐insulating substrates has been investigated by TEM and SIMS profiling. Annealing at 350u2009°C for variable periods was found to produce rapid outdiffusion of Cr into regions of near‐surface damage induced by strain effects at the interface and subsequent diffusion of Au into the GaAs.

Thermal diffusion of tin in GaAs from a spin‐on SnO2/SiO2 source

The thermal diffusion of Sn in GaAs from a spin‐on SnO2/SiO2 source is described. The processing steps leading to reproducible electrical charcteristics are presented. Electrical measurements, secondary‐ion mass spectroscopy, and Rutherford backscattering analysis have been used to study the diffusion during various processing sequences. The results show that this source can make Sn atoms available for diffusion at very low temperatures and produce heavily doped, shallow n+ layers that may be of interest for GaAs field‐effect transistor technology.