Research Article

Nonradiative and Radiative Recombination in CdS Polycrystalline Structures

Table 2

Parameters of different type CdS samples.

ParameterSample type
I-typeII-typeIII-type

Technological regime = 220 °C 
= 60 min
= 260 °C
= 75 min
= 260 °C
= 80 min
Equilibrium density of carriers (CdS base) << 1013 cm−3 ≥ 1.5 × 1013 cm−3 ≥ 1.5 × 1013 cm−3
Cu2S-CdS heterostructure
(pulsed capacitance-BELIV)
Capacitor-like [18], insulator-specific state of CdS base materialJunction-like [18], generation current component in CdS base is pronouncedJunction-like [18], barrier charging current prevails
Activation energy of the dominant traps (DLTS, PIS)n/a
[19]
1.17 ± 0.02 eV;
1.65 ± 0.02 eV;
2.19 ± 0.04 eV
[19]
0.22 ± 0.02 eV;
0.40 ± 0.02 eV;
[19]
1.21 ± 0.02 eV;
1.56 ± 0.02 eV;
2.19 ± 0.04 eV
[19]
0.22 ± 0.02 eV;
0.31 ± 0.02 eV;
[19]
1.19 ± 0.02 eV;
1.62 ± 0.02 eV;
2.19 ± 0.04 eV
Grain size/homogeneity of distribution crystal grains in CdS substrate (MCI)<1 μm
inhomogeneous
2–10 μm
homogeneous
2–10 μm
inhomogeneous
Instantaneous lifetime of the initial decay (MW-PC)3 ns 5 ns10 ns
Instantaneous lifetime of the asymptotic decay (MW-PC)>100 μs>800 μs>400 μs
Ratio of the amplitudes of the asymptotic to the initial MW-PC decay = / 0.250.010.04
Instantaneous lifetime of the initial PL decay
G-PL peaked at 500 nm (TR-PL)
5 ns
PL photo-quenching observable
2 ns
the strongest PL photo-quenching
2 ns
strong PL photo-quenching
Instantaneous lifetime of the asymptotic decay for R-PL peaked at 700 nm (TR-PL)n/a40 ns150 ns
Ratio of the G-PL & R-PL intensities
/ (MCI-PLS)
<1≥1≥1.5
Fractional SER index α (MW-PC)0.200.160.17
Fractal factor (SER)0.170.130.14