Evidence of a donor-acceptor type transition in CuGaSe2

Abstract

Measurements of spectrum shift are made by means of time resolved spectroscopy (T.R.S.) over a broad emission band of CuGaSe2, peaked at 1.59 eV with a width of 40 meV (at liquid helium temperature). The behaviour of the decay is measured at 4 K for different emission band energies. We will show that the experimental results are in agreement with a donor-acceptor model. From the shift of the spectra in T.R.S. we can fit : — the Bohr-half-radius value RB = 5.6 Å (the shallowest centre is at least at 70 meV) ; — the maximum radiative transition probability WMAX = 108 s-1; — the value hv ∞ = 1.53 eV. The theoretical and experimental decay curves are in good agreement for a preponderant impurity concentration of N = 8 × 1017/cm3. By using these various parameters we observe that theoretical and experimental T.R.S. spectra are consistent