Measurements of Compositional Change in Semi-Insulating GaAs Single Crystals by Precise Lattice Parameter Measurements

Abstract

Precise lattice parameter measurements have been made for semi-insulating GaAs, and it is found that the lattice parameters vary greatly (order of 10-4 Å) among GaAs wafers and in a wafer. This variation of lattice parameter is closely related to the threshold voltage of the FETs, which are made by direct ion implantation on the crystal. The change of the lattice constant is probably caused by the interstitial As atoms, and a slight change of crystal growth condition may cause its variation in the wafer. Variation of the As concentration affects the threshold voltage of MESFETs when they are made by direct ion implantation.

Study on fundamental defects and their effect on GaAs device properties

“…While many reports concerning the origin of Vth scattering on the substrate have appeared else-where, the notable results may be summarized as follows ; (i) dislocations [2,3], (ii) residual C concentration [4], (iii) local EL2 concentration [5], and (iv) local lattice strain caused by the deviation from stoichiometry [6]. A contrary result has also been reported, in that no dislocation effect on Vth scattering was demonstrated [7].…”

“…The greater negative Vth shift is attributable to the higher (SiGa -SiAs ) net concentration around the dislocations. The reaction determining whether Si replaces Ga site or As site is expressed [28] (6) where ni is intrinsic carrier concentration.…”

“…Equation (6) implies that the higher the sheet carrier concentration ( [SiGa 1 / [S1AS J ratio ), the higher the [vGaJI[vAsJ concentration ratio.…”

Coulometric Determination of Arsenic in Undoped LEC SI ‐ GaAs Crystals

“…In order to evaluate the deviation from stoichiometry of III-V compound crystals, the following approaches have been made: coulometric titration (4,5), lattice parameter measurement (6), ion beam scattering (7), photoluminescence measurement (8), and x-ray intensity measurements of the quasi-forbidden reflection (9). Among these methods, coulometric titration presents a unique method for absolute measurements according to Faraday's taws, though it has such demerits as the necessity of complicated pretreatments and resultant destruction of specimens.…”

Electrical Characterization of Ion Implantation into GaAs: Topography and Depth Profiles

“…Such wafers are often laterally inhomogeneous and so should be characterized over the whole surface, which is practical only with automated techniques. In recent years, the properties exploited by nondestructive topographic techniques include: photoassisted resistance (1)(2)(3)(4)(5), microwave photoeonductance (6, 7), photoluminescence (8,9), cathodoluminescence (10), photoabsorption (11,12), and x-ray scattering (13)(14)(15). Furthermore, a commercial apparatus is available for topographic device measurements, such as transconductance and pinchoff voltage.…”