The 3d transition metals (TM’s) from Cr to Cu introduced into InP by diffusion are studied using low temperature photoluminescence (PL). Luminescence bands from Mn, Co, and Cu are observed whereas for the remaining TM’s, Cr, Fe, and Ni, no optical effects related to the diffused species are detected. This behavior is found to correlate with electrically active, compensating deep acceptor levels found for Mn, Co, and Cu in C-V measurements, but not for the other TM’s. For Mn diffusions at 800 °C deep level PL peaking at 1.15 eV ascribed to substitutional Mn2+In is observed. For the case of Cu three different PL bands are found peaking at 1.2, 1.17, and 0.99 eV, respectively. It is speculated that the 1.0-eV band may arise from CuIn centers. The higher energy bands arise from Cu-related complexes. Reasons for the electrical and PL activity of Mn and Co, but not for the adjacent fast diffusing TM’s Cr and Fe which are electrically active in growth doped material, are discussed in terms of the particularly deep acceptor levels formed by Mn and Co.
A new Cu-related photoluminescence band in InP is reported. It consists of a sharp zero-phonon line at 1.2889 eV with sharp LO and 'gap mode' local phonon replicas to lower energy superimposed on a broad vibronic background. Zeeman studies show that the recombination process arises from an exciton bound to a neutral isoelectronic centre. Electron and hole g-values of 1.27 and 2.12 respectively are deduced, with both electron and hole having spin 1/2. The very strong diamagnetic shift of the spectrum is found to be equal to that of a shallow donor electron in InP. This demonstrates clearly that the hole is tightly bound in the short-range potential of the centre with binding energy EB
h=127.5 meV and that the electron is then weakly bound in the Coulomb field of the hole (EB
e=7.3 meV), so that the overall behaviour is of an isoelectronic donor. The thermal activation energy of the vibronic sideband of the luminescence is found to be 135+or-10 meV, in good agreement with the spectroscopic value of the hole binding energy.
Iron has been diffused into GaAs from the vapour phase. Use has been made of radiotracer techniques, electrical measurements and electron paramagnetic resonance to investigate the properties of the material after diffusion. The iron is found to behave as a net acceptor in material that was originally n-type but its electrical activity is only about 0.5. It is concluded that the diffusion mechanism is primarily interstitial but that most of the iron in the bulk of a specimen is substitutional. Close to the surface of a diffused slice the situation is less clear and it seems likely that the iron is incorporated in the form of some complex.
The residual carbon acceptor concentration [CAs] in three radio-tin-doped, liquid encapsulated Czochralski, GaAs single crystals was estimated from a plot of carrier concentration versus tin concentration determined by radio-tracer counting. Local vibrational mode absorption of CAs in the samples was measured at room temperature and a calibration factor of 8±2×1015 cm−1 obtained. A comparison of this with other determinations suggests that the true calibration factor lies between 8 and 11×1015 cm−1 and that earlier, larger calibration factors should be discounted.
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