Results of optical absorption and photoconductivity measriremente in the 0.1 to 2.4 eV range of GaP crystaln irradiated with 7.5 and 50 MeV electrons are presented. The absorption of irradiated crystals near the edge can be represented by two exponential regions. In the free carrier absorption region one can observe as a result of irradiation a decrease of the power index p in the dependence a -DJ. Photoconductivity with long-time relaretion takes place in the spect,ral interval where
According t o /l/, the equilibrium state of a heterosystem (HES) is the coherent state at small film thickness and the incoherent one with edge misfit dislocations (MD) lying exactly in the interface (IF) after the film thickness exceeds some critical value. In both states the HES is bent, but the substrate must flatten if one removes the film because the sources of internal stresses are removed simultaneously with film removal and extra half-planes connected with the MD in the bicrystal become the regular crystal planes of the substrate.Experiments made by us with Ge-GaAs and ZnS-GaAs structures (see solid lines on Fig. 1 and 2) show, however, that the GaAs substrate remains bent after film removal, and to obtain a flat substrate it is necessary to remove an additional substrate layer adjacent to the IF /2/.(100) or (110) GaAs substrates at 500 OC. The HES ZnS-GaAs was VPE grown on GaAs substrates at 870 OC. The substrate thickness was 250 pm. The HES curvature at was measured by the profilograph M-201. Fig. 1 and 2 show the change of -a during layer-by-layer film e t c h w (d is the distance from the IF). For each system measurements have been made on identical samples obtained in the same technological process; one was the control sample and the other was r-irradiated (Co 1. The substrates of unirradiated HES are found t o be bent after the film removal and the thickness of the plastically deformed layer h is rather large. The latter essentially decreases in irradiated HES. Thus, it seems that the irradiated HES is nearer t o the equilibrium state than the unirradiated one.The investigated HES Ge-GaAs was obtained by Ge vacuum deposition on 60 1) Prospekt Nauki 115, 252028 Kiev, USSR.
The results are presented of formation and annealing of defects in InP crystals at 1 to 50 MeV electron irradiation. The recovery of electrical properties in the range of 77 to 970 K during annealing processes is studied. Five low temperature annealing states in n‐InP and the reverse annealing in p‐InP are observed at 77 to 300 K. Pour annealing stages at temperatures higher than 300 K are present. When the electron energy is increased more complicated thermostable defects are formed, and at 50 MeV electron energy besides of the point defects defect clusters are formed, which anneal at temperatures of 800 to 970 K. It is shown that the peculiarities of the Hall mobility at irradiation and annealing are caused by the scattering centres Ec — 0.2 eV. The “limiting” position of the Fermi level in electron irradiated InP crystals is discussed.
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