Defects in Weakly Damaged Ion-Implanted GaAs and Other III–V Semiconductors

Abstract

Under definite implantation conditions (small ion masses, sufficiently small ion fluences, and high implantation temperature) in III–V compounds weakly damaged layers are produced, which exhibit characteristic properties near the optical edge and an only slight increase of dechanneling of backscattered light ions. Especially for GaAs, InP, and GaP an exponential dependence of the near edge absorption coefficient on the photon energy according to K ∼ exp (ħω/E1) with E1 = 0.52 eV for GaAs, 0.33 eV for InP, and 0.6 eV for GaP is observed. From theoretical considerations it is concluded that this behaviour is connected with the existence of high concentrations of complexes containing antisite defects and vacancies. Combining optical measurements with TEM and measurements of the temperature dependence of the dechanneling gives further information about the structure of weakly damaged GaAs layers. The results of a complex analysis of weakly damaged GaAs and other III–V compound layers and first ideas about the damage structure in such layers are discussed.

Damage formation and optical absorption in neutron irradiated SiC

“…4, to E 02 = 0.23 eV for the highest. The occurrence of two different exponential ranges of the absorption coefficient versus the photon energy was also found in ion implanted GaP [10]. In this material the parameter E 02 exhibits a pronounced [10] and E 01 a very weak dependence on the defect concentration [10,23].…”

“…The occurrence of two different exponential ranges of the absorption coefficient versus the photon energy was also found in ion implanted GaP [10]. In this material the parameter E 02 exhibits a pronounced [10] and E 01 a very weak dependence on the defect concentration [10,23]. Also in the case of ion irradiated silicon the divacancy absorption band already mentioned above is superimposed by an exponentially increasing background absorption the slope of which varies only slightly with the defect concentration; the spectral range close to the direct band gap was not resolved [8].…”

“…[7,8]) and III-V compound semiconductors (see e.g. [9][10][11]). Point defect complexes and amorphous structures often exhibit a different spectral dependence of the absorption coefficient and a different refractive index change, which may allow separation of the contributions of the two structures within the implanted layers [4,12].…”

“…It was found for B ion implanted SiC that the spectral dependence of the absorption coefficient seems not to change and increasing defect concentration results only in an increase of its absolute value [3]. Contrary to SiC, in GaAs both the spectral dependence and the absolute value of the absorption coefficient vary with the defect concentration introduced by ion [10] or neutron irradiation [13]. In the case of low defect concentrations and correspondingly low absorption coefficients, the study of ion implanted layers is limited due to their small layer thicknesses.…”

“…In the direct materials GaAs and InP only one exponential increase of the absorption coefficient with photon energy is found with the parameter E 02 being clearly dependent on the defect concentration [10,11].…”