Conduction Band Of CdS Research Articles

Tunneling currents in the copper sulfide/cadmium sulfide heterojunction

The parameters controlling the photovoltaic properties of the Cu 2 S/CdS heterojunction have been investigated. It is found that the behavior of the short-circuit current and the open-circuit voltage are describable in terms of a deep, donor-like level in the CdS region adjacent to the metallurgical interface. When tunneling from this level into the Cu 2 S is the mechanism controlling the current flow, the J_{SC}-V_{OC} characteristics of the device are described by the equation J_{SC} = J_{00} \exp (a_{i}(E_{I} - \Phi_{T}_{0})) {\exp (a_{i}q V_{OC})-1} where J SC is the short-circuit current, J 00 is the current preexponential factor, \Phi _{T}_{0} is the zero-bias barrier height in the CdS, E I is the ionization energy of the deep donor, V OC is the open-circuit voltage, and a i is a tunneling factor dependent on the net positive charge density in the CdS near the interface. The relative probability of tunneling from this level to the Cu 2 S is derived, as is the probability of tunneling from the level to the CdS conduction band. The photocapacitance effects observed in this junction are attributed to the joint action of this level and an acceptor state due to copper in the CdS. Combining the results from the tunneling calculation, the J_{SC}-V_{OC} data, and the quenching spectra of the photocapacitance, the ionization energy of the donor level is determined to be 0.45 eV and the density of these levels exceeds 1019cm-3near the interface. The donor level acts as a recombination center, reducing J SC , and as a tunneling center, reducing V OC . Since these levels exist in junctions produced by the dipping method or by the dry method, they set fundamental limits to the efficiency of devices fabricated using these methods.

Enhancement of donor electronic Raman scattering in CdS

Resonance enhancements of electronic Raman scattering due to shallow donors (substitutional Cl and F) in CdS are reported. The experimental results are interpreted quantitatively in terms of "two-step" electronic Raman processes. The resonant intermediate states are the top valence bands and bottom conduction band of CdS and also excitons bound to the donors. The relative contributions of the valence bands to the scattering cross section have been calculated with Hopfield's quasicubic model. It is demonstrated that by utilizing resonance enhancements donor electronic Raman scattering can be observed with only a few milliwatts of laser power in CdS containing less than ${10}^{16}$ ${\mathrm{cm}}^{\ensuremath{-}3}$ of donor atoms.

Effect of piezoelectric potential scattering on the microwave faraday effect in n‐CdS

AbstractThe theory of free‐carrier Faraday effect in semiconductors previously developed by Donovan and Webster for lattice and impurity scattering is extended to the case of n‐type CdS, taking into account piezoelectric and deformation potential scattering. The high frequency magnetoconductivity tensors are derived considering the detailed structure of the conduction band of CdS. The Faraday rotation measurements in n‐type CdS along the c‐axis are performed at liquid nitrogen temperature and room temperature at 24 GHz. The experimental results are found to agree well with the theory, for β = p/a = 1.9, where a and p being the deformation potential and piezoelectric scattering coefficients at T = 90 °K, respectively.

Space-charge-limited (SCL) effects in thin, Cu compensated CdS structures

A theory which is presented for handling one carrier space-charge-limited effects in thin, compensated high-resistivity layers, includes both the voltage drop across a high resistivity region and a π junction. Good agreement is obtained between the theory and the measured I– V characteristics of Cu-compensated CdS. A trapping energy state 0·37 eV below the CdS conduction band and of density 1∼2×10 15 cm −3 is identified.