Local electronic structure of phosphorus-doped ZnO films investigated by X-ray absorption near-edge spectroscopy

Direct evidence for Sb as a Zn site impurity in ZnO

“…In order to explain the p-type character of ZnO following As and Sb doping it was suggested that the acceptor action is actually due to As Zn -2V Zn or Sb Zn -2V Zn complexes, where an As or Sb atom occupies a Zn "anti-site" and is decorated with two Zn vacancies [16][17][18][19]. However, a complex acceptor model for P, As or Sb in ZnO is strongly disputed by some authors [20][21][22][23][24].Obviously knowledge on the lattice location of the group V elements in ZnO is crucial in order to assess the related mechanism of p-type doping. We have previously determined the lattice sites of ion implanted As by means of conversion electron emission channeling from radioactive 73 As [25][26][27] and found that As does not occupy substitutional O sites but mostly substitutional Zn sites.…”

“…In order to explain the p-type character of ZnO following As and Sb doping it was suggested that the acceptor action is actually due to As Zn -2V Zn or Sb Zn -2V Zn complexes, where an As or Sb atom occupies a Zn "anti-site" and is decorated with two Zn vacancies [16][17][18][19]. However, a complex acceptor model for P, As or Sb in ZnO is strongly disputed by some authors [20][21][22][23][24].…”

Lattice location of the group V elements Sb, As, and P in ZnO

“…Unfortunately our experiments cannot settle the interesting issue whether substitutional P, As and Sb on oxygen sites ("chemical acceptor model"), as is often assumed 10,11,26,29,48 , or P Zn −2V Zn , As Zn −2V Zn , and Sb Zn −2V Zn complexes ("complex acceptor model") 12,[44][45][46][47] are responsible for the acceptor action. The fact that implanted P, As and Sb prefer the substitutional Zn sites is clearly a strong argument in favor of the complex acceptor model.…”

“…In the meantime, As-doped p-type ZnO has been produced by means of pulsed laser deposition 7,[9][10][11][12] , hybrid beam deposition 13,14 , evaporation and sputtering 15 , ion implantation 16,17 , radiofrequency (RF) magnetron sputtering 18 , and metal-organic chemical vapor deposition (MOCVD) 19 , and devices include ultraviolet (UV) 14,17 and visual-infrared light emitting diodes (LEDs) 19 . Succesful doping methods for P include excimer laser processing 8 , diffusion 20,21 , RF sputter deposition [22][23][24][25][26] , molecular beam epitaxy (MBE) 27 , MOCVD 28 , and laser ablation 29 . However, so far mostly rectifying diodes have been demonstrated from p-ZnO:P 8,21,24,25 and only weak electroluminescence in the visible 8 .…”

“…Also based on DFT results, the experimentally observed ptype behaviour was attributed to the formation of electrically active acceptor complexes of the type P Zn −2V Zn , As Zn −2V Zn or Sb Zn −2V Zn, first predicted by Limpijumnong et al [44][45][46][47] for As and Sb and later by Shen et al 12 for P, the "complex acceptor model". While this concept is finding more and more acceptance 6,16,18,25,28,32,36,[38][39][40][41][42] , it is strongly disputed by others who support the point of view that P, As or Sb in ZnO act as simple chemical acceptors that replace oxygen 10,11,26,29,48 , the "chemical acceptor model". [52][53] .…”