Indium Acceptors Research Articles

Activation energies of the InSi‐Siidefect transitions obtained by carrier lifetime measurements

Light‐induced degradation (LID) is investigated in indium doped silicon by time and temperature dependent carrier lifetime measurements. Different transitions rates and activation energies were measured and interpreted within theASi‐Siidefect model. The case of indium acceptors is compared to the case of boron. Results are discussed within the frame of a comparison betweenASi‐SiiandASi‐Feidefects. It was found that reported dependencies of the transitions rates of theASi‐Siidefect on the hole density support defect models which are based on defect configuration changes. An in‐depth explanation of theASi‐Siidefect model is given and possible errors related to the measurement of transition rates are discussed.

Perturbed angular correlation spectroscopy of hydrogen-passivated indium acceptors in silicon

Hydrogen-passivated 111In atoms in boron-doped silicon samples are investigated with respect to their thermal properties by the perturbed angular correlation method. The temperature dependence of one of the electric field gradients induced by the formation of close 111InH pairs reflects the electron capture decay of 111In into 111Cd. A model based on the thermally activated population of a 111CdH acceptor fits quantitatively to the temperature data, yielding an acceptor level close to 0.1 eV above the valence band.

Electron capture coefficient of neutral indium and pair recombination in compensated silicon

Indium-doped silicon, well compensated with phosphorus, was illuminated in order to neutralise the indium acceptors. The photoluminescence spectra and their decays were measured for temperatures between 4K and 135K. Below about 60K the spectra showed a phosphorus-indium pair recombination which was fast and had a recombination rate constant Wmax approximately=104 s-1. Above 80K the conduction-band-indium transition dominated and gave a value for the electron capture coefficient Bca=2*10-15 cm3 s-1. Approximate quantum mechanical calculations of the radiative part of Bca were performed both for the phononless and the phonon-assisted transitions. The results of these calculations agreed within the expected accuracy with the experimental results and suggested that the electron capture of indium is a radiative process.

Photoinduced Infra-red Absorption and Luminescence in Indium-doped Silicon

Silicon, doped with indium and phosphorus to 1016 cm-3 and well compensated, was illuminated to neutralize the indium acceptors. The time-dependent neutral acceptor concentration was measured by the infra-red absorption of the valence band-indium transition. The decay of the absorption, after interrupting the exciting illumination, was nearly independent of the temperature between 28 K and 80 K. The photoluminescence spectrum shows that phonon-less conduction band-to-indium transitions dominate also at 28 K. The luminescence decay confirms that the recombination is a bimolecular process.

Indium bound exciton luminescence in silicon

A high-resolution photoluminescence study is presented of the bound exciton line and its 4 meV low energy satellite in Si:In. The excitation and temperature dependence and the decay times suggest that the satellite line originates from the decay of an exciton bound to the indium acceptor. We tentatively correlate this line with excitations of the final state indium acceptors into a vibrational excited level.

The effect of removal of gallium, thallium and indium acceptors and bismuth, antimony and arsenic donors in ion-bombarded silicon surface layers

The effect of removal of gallium, thallium and indium acceptors and bismuth, antimony and arsenic donors in ion-bombarded silicon surface layers

Stress-induced mixing of the spin-orbit-split acceptor states of silicon

A theoretical treatment of the stress-induced mixing of the impurity states arising from the top of the ${p}_{\frac{3}{2}}$ valence band with those of the spin-orbit-split ${p}_{\frac{1}{2}}$ band of silicon is presented. The nonlinear stress dependence of the $2{p}^{\ensuremath{'}}$ line of boron, aluminum, gallium, and indium acceptors in silicon is examined. The ratio of the deformation potential constants of the excited state of the $2{p}^{\ensuremath{'}}$ line with the spin-orbit splitting ${\ensuremath{\lambda}}_{e}$ is determined. The nonlinear stress dependence of one of the components of the 23-meV electronic Raman line of boron acceptors in silicon determined by Cherlow, Aggarwal, and Lax is shown to be consistent with this transition being from the fourfold acceptor ground state to its spin-orbit-split twofold partner state; this transition has been observed for the first time as a transition in the far infrared.

Electron capture coefficient of neutral indium in silicon

Silicon, doped with indium and phosphorus to 10 16 cm −3 and well compensated, was illuminated by a halogen lamp, causing neutralization of the indium acceptors. The neutral acceptor concentration was determined by infra-red absorption measurements. From the decay of absorption, after interrupting the exciting illumination, the electron capture coefficient of neutral indium was calculated as 2 × 10 −15 cm 3 sec −1 at 77 K.

Optical Study of Silicon Doubly Doped with Boron and Indium Acceptors

The external and internal absorption spectra of silicon doubly doped with boron and indium acceptors is studied. The observed broadening of the boron absorption lines in Si(B, In) is explained by neutral impurity scattering. The presence of indium in the Si(B, In) crystal lattice modifies the valence band Bloch states and hence the configuration interaction between the internal acceptor states and the degenerate P3/2 valence band Bloch states. This modification is found responsible for the observed features of the boron 2p′ internal line in Si(B, In).

The photon-ionization cross-section of indium acceptors in silicon

Optical absorption and Hall data for In-doped-Si crystals have been used to determine the photo-ionization cross-section σ I ( hυ). The spectral dependence accords with prior reports, and with simple deep impurity models. However, we find a maximum σ I of 3.3 × 10 -17 cm 2, several times smaller than previous estimates, thus removing the need for a large effective-field correction.

Optical Phonon-Assisted Transitions in Deep Acceptor Impurities in Silicon

The coupling between the lattice and the impurity bound carrier for deep monovalent acceptors in silicon, such as gallium and indium, is found to be stronger than for the shallower boron impurity. This suggests the possible existence of optical phonon-assisted transitions associated with these deep impurities. Such transitions are observed in the absorption spectrum of indium-doped silicon. The phonon-assisted transitions are superimposed on the photoionization continuum transitions of the indium acceptors. Interference effects between the phonon-assisted transition and the transition to the continuum states modify the position and line shape of the transitions. Using the phonon dispersion curves for silicon, interpretation of the results is presented. An estimate of the strength of the electron–phonon coupling in indium-doped silicon is obtained.

Photoconductivity Associated with Indium Acceptors in Silicon

Experiments are described in which excess free holes are generated in $p$-type silicon by the photo-ionization of neutral indium acceptors (${E}_{a}=0.155$eV), and of the subsequent hole capture by ionized indium centers. Using chopped monochromatic radiation of small intensity for illumination, a comparison has been made of dc dark conductivity and of chopped photoconductive responsivity in order to determine the excess hole lifetime and the ionized-acceptor capture cross section as a function of temperature. For samples with an indium concentration in the range 5\ifmmode\times\else\texttimes\fi{}${10}^{15}$ to 5\ifmmode\times\else\texttimes\fi{}${10}^{17}$ ${\mathrm{cm}}^{\ensuremath{-}3}$, the hole-capture cross section decreases by a factor of 100 in the temperature range 70-180\ifmmode^\circ\else\textdegree\fi{}K. This cross section is \ensuremath{\sim}2\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}13}$ ${\mathrm{cm}}^{2}$ between 70 and 120\ifmmode^\circ\else\textdegree\fi{}K, a range in which the sticking probability is appreciable for capture into the first excited states of the acceptor. A cross section of \ensuremath{\sim}2\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}15}$ ${\mathrm{cm}}^{2}$ at 180\ifmmode^\circ\else\textdegree\fi{}K is found in agreement with predictions that capture at this temperature can occur only into the ground state of the acceptor. The spectral dependence of photoconductive response in "optically thin" samples is compared with the quantum efficiency expected from optical-absorption measurements and from theoretical models of indium acceptors; it is found that the photoconductive efficiency is anomalously small within the range $0.155<h\ensuremath{\nu}<0.24$ eV at the lower temperatures.

Photoexcited Electron Capture by Ionized and Neutral Shallow Impurities in Silicon at Liquid-Helium Temperatures

The capture rates for photoexcited electrons due to ionized phosphorus, arsenic, antimony, and bismuth donors as well as neutral boron, aluminum, gallium, and indium acceptors in silicon have been determined in the liquid-helium temperature region, using combined optical and paramagnetic-resonance techniques. The ionized-donor capture rates exceed by about an order of magnitude the values predicted from the theories of Lax and of Ascarelli and Rodriguez for capture of thermalized electrons. The capture rates are independent of temperature between 1 and 4\ifmmode^\circ\else\textdegree\fi{}K, at variance with both theories, and their dependence on the ionization energy of the different donors also does not conform to the theoretical predictions. These results, as well as photoconductivity measurements as a function of charged-impurity concentration, demonstrate the inadequacy of any existing model of the low-temperature donor capture process for photoexcited electrons in silicon. Possible explanations of the results in terms of nonrandom impurity clusters or capture from hotelectron states are presented. The neutral-acceptor rates are about two orders of magnitude smaller than those of the ionized donors, are also independent of temperature between 1 and 4\ifmmode^\circ\else\textdegree\fi{}K, and show a small dependence of about ${I}^{\frac{1}{2}}$ on the hole ionization energy of the impurities, compared with expected ${T}^{\frac{1}{2}}$ and ${I}^{\ensuremath{-}\frac{3}{2}}$ dependences from the theory for thermalized-electron capture by neutral centers. As in the case of the ionized donors, no presently available model appears adequate to explain the results.