Temperature dependence of the band gap of zinc nitride observed in photoluminescence measurements

Abstract

We report the photoluminescence properties of DC sputtered zinc nitride thin films in the temperature range of 3.7–300 K. Zinc nitride samples grown at 150 °C exhibited a narrow photoluminescence band at 1.38 eV and a broad band at 0.90 eV, which were attributed to the recombination of free carriers with a bound state and deep-level defect states, respectively. The high-energy band followed the Varshni equation with temperature and became saturated at high excitation powers. These results indicate that the high-energy band originates from shallow defect states in a narrow bandgap. Furthermore, a red-shift of the observed features with increasing excitation power suggested the presence of inhomogeneities within the samples.

Ultrafast Photocarrier Dynamics and Nonlinear Optical Absorption of a Layered Quaternary AgInP2S6 Crystal

“…31 Defect-assisted emission usually involves a saturation effect as the excitation intensity increases since the limited density of trapping states in the extrinsic energy levels (e.g., induced by defect or impurity) can be fully populated, resulting in a saturation of the PL emission intensity. 30,32 The very large width of the PL emission spectrum observed here also supports that the emission is related to deep-level defects. 30 Since the emission peak is energetically lower than the band gap, the carriers injected by interband absorption should first relax to the bottom of the energy band and then be transferred from the conductor band minimum (CBM) to the defect energy levels for radiative recombination (i.e., transition between defect bands and the valence band), as schematically shown in Figure 3.…”

“…PL spectroscopy is an effective avenue to access the carrier relaxation process in the band structure. 30 First, the PL emission spectra were measured under CW laser excitation at wavelengths of 405 and 532 nm, separately. The emitted light was collected from the surface of the sample and focused onto a fiber spectrometer (Ocean Optics) after passing through the corresponding notch filter.…”

Epitaxial Zn3N2 thin films by molecular beam epitaxy: Structural, electrical, and optical properties

“…All measured samples show optical band-gap energies between 1.05 and 1.37 eV, being in agreement with most of the previous literature. 10,15,[25][26][27][28][29][30][31][32][33][34][35][36][37][38] Burstein and Moss 43,44 described the influence of the carrier concentration in semiconductors on their optical band-gap. The displacement of the Fermi level into a parabolic conduction band leads to a band-gap shift according to (8) where denotes the electron concentration.…”

“…[14][15][16][17][18][19][20][21][22] Although some band-gap studies on Zn 3 N 2 estimated values of 2.9-3.4 eV, 14,16,23,24 most of the recent studies and theoretical calculations, including photoluminescence measurements, find values in the 0.8-1.5 eV range. 10,15,[25][26][27][28][29][30][31][32][33][34][35][36][37][38] The reason for this large discrepancy lies probably in the tendency of Zn 3 N 2 to oxidize in ambient conditions, 34,39 which could lead to a strong overestimation of the band-gap energy, as masked by the presence of ZnO (with a band-gap in the order of 3.3 eV 40 ). However, even in recent literature, the reported values display a large spread.…”

Confinement Effects and Charge Dynamics in Zn3N2 Colloidal Quantum Dots: Implications for QD-LED Displays

“…Zinc nitride (Zn 3 N 2 ) is a nontoxic, low-cost, and earth-abundant semiconductor that has not yet been exploited as much as group III nitrides because of the difficulties in the preparation of high-quality Zn 3 N 2 crystals . Studies of the structural, electrical, and optical properties of this material have been largely limited to thin film geometries, which have been prepared by a variety of methods including metal–organic chemical vapor deposition, RF–molecular beam epitaxy, direct reaction by annealing metallic zinc in an ammonia atmosphere, pulsed laser ablation, molten salt potentiostatic electrolysis of zinc, as well as DC , and RF , magnetron sputtering. A wide range of optical bandgap values have been reported in these studies (varying from ∼1.0 to 3.2 eV), generating some controversy about the origin and true nature of the electronic transitions.…”