Experimental observation on the Fermi level shift in polycrystalline Al-doped ZnO films

Abstract

The shift of the Fermi level in polycrystalline aluminum doped zinc oxide (AZO) films was studied by investigating the carrier density dependence of the optical band gap and work function. The optical band gap showed a positive linear relationship with the two-thirds power of carrier density ne2/3. The work function ranged from 4.56 to 4.73 eV and showed a negative linear relationship with ne2/3. These two phenomena are well explained on the basis of Burstein-Moss effect by considering the nonparabolic nature of the conduction band, indicating that the shift of Fermi level exhibits a nonparabolic nature of the conduction band for the polycrystalline AZO film. The variation of work function with the carrier density reveals that the shift of the surface Fermi level can be tailored by the carrier density in the polycrystalline AZO films. The controllability between the work function and the carrier density in polycrystalline AZO films offers great potential advantages in the development of optoelectronic devices.

Probing the doping mechanisms and electrical properties of Al, Ga and In doped ZnO prepared by spray pyrolysis

“…This is consistent with the observed lower carrier concentrations measured in SP deposited films compared with zinc rich environments of well-studied vacuum techniques such as PLD and magnetron sputtering -where carrier concentrations in the order of 10 21 cm -3 are reported. 47,48 As the Fermi energy rises with increasing free carrier concentration 49 , the formation energy of a dopant occupying a substitutional site increases. In parallel, the formation energy of an Al Zn V Zn acceptor hybrid defect decreases and, in oxygen rich conditions, falls below that of the Al Zn.…”

Indium-free Cu/fluorine doped ZnO composite transparent conductive electrodes with stretchable and flexible performance on poly(ethylene terephthalate) substrate

“…The increase in carrier concentration can be understood by the carrier injection from Cu layer into FZO layer since the work function difference between Cu and FZO. Copper has a work function of ˚ ≈ 4.5 eV [30] and FZO has a work function of ˚ ≈ 4.85 eV [31], as shown in Fig. 7.…”

Photoreflectance investigation of band gap renormalization and the Burstein–Moss effect in Si doped GaN grown by MOVPE

“…Further improvements in high performance of GaN-based devices call hence for an accurate and systematic understanding of basic physical modification undergone by the material due to doping. In heavily doped semiconductor, one of the most important material parameter, namely the fundamental band gap, is frequently affected by high electron concentration as a result of a two competing effects [4][5][6][7][8][9][10][11][12]. First, the well-known Burstein-Moss (BM) band-filling effect, which shifts the absorption onset to higher energies with increasing carrier concentration [4][5][6][7][8][9][10][11][12][13][14].…”

“…In heavily doped semiconductor, one of the most important material parameter, namely the fundamental band gap, is frequently affected by high electron concentration as a result of a two competing effects [4][5][6][7][8][9][10][11][12]. First, the well-known Burstein-Moss (BM) band-filling effect, which shifts the absorption onset to higher energies with increasing carrier concentration [4][5][6][7][8][9][10][11][12][13][14]. The second phenomenon, called band gap renormalization (BGR), decreases the fundamental band gap energy with increasing carrier density due to many-body interactions [4][5][6][7][8][9][10][11][12]15].…”