Nitrogen-doped p-type ZnO films prepared from nitrogen gas radio-frequency magnetron sputtering

Abstract

Wide band gap nitrogen-doped p-type ZnO films are prepared by radio-frequency magnetron sputtering from a 99.99% purity ZnO target. The sputtering gas is Ar mixed with various flow rates of nitrogen gas. Hole concentrations increase from 1.89ϫ 10 15 to 2.11ϫ 10 19 cm −3 as the N 2 flow rate decreases from 15 to 6 SCCM ͑SCCM denotes cubic centimeter per minute at STP͒, i.e., increasing N 2 flow rate above 6 SCCM decreases the p-type carrier concentration. Microphotoluminescence ͑PL͒ spectra peaks are in the near-UV range and change from 384 nm ͑3.23 eV͒ to 374 nm ͑3.32 eV͒ with increasing N 2 flow rate. The PL peaks agree with the band gap of bulk ZnO, which comes from the recombination of free excitons. Raman spectra show six peaks: 436 ͑E 2 high-frequency phonon mode for undoped ZnO film͒, 581 ͓A 1 ͑LO͒ mode in ZnO:N film͔, 275, 508, 640, and 854 cm −1 ͑local vibrational modes of Raman features in N-doped ZnO film͒.

THE LEVEL OF SELF-COMPENSATION OF ZnO CODOPED BY NITROGEN AND ALUMINUM

“…З виразу для концентрації електронів (3) зна-ходимо енергію рівня Фермі (6) що, знаючи n(Т), дозволяє знайти температурні залежності ∆μ (Т), показані на Рис. 6.…”

“…По-казано, що короткочасну високу концентрацію дірок (до 10 19 см -3 ) в оксиді цинку можна досяг-ти застосовуючи легування останнього елемен-тами V групи [6,7]. Проте ефект самокомпен-сації має місце і при легуванні ZnO акцептора-ми.…”

Evolution of crystal structure of Zn:N films under high temperature

“…Zn 3 N 2 powder could be obtained from a nitridation reaction of Zn powder with NH 3 gas at the temperature of 600 °C [14]. In addition, Zn 3 N 2 phase in ZnO:N thin films grown by sputtering could be examined by X-ray diffraction (XRD) [1,15]. Then, it is expected that the first mechanism to obtain p-type ZnO is the formation of Zn 3 N 2 at a suitable temperature.…”

“…Among many materials, as a same material of n-type ZnO in window layer of the CIGS solar cell, p-type ZnO has caught many interests despite the difficulty of the fabrication. Generally, p-type ZnO was carried out by doping group-V element such as N [1][2][3][4][5][6], P [7,8], As [9], and Sb [10] into oxygen sites of ZnO structure. Due to the smallest atomic radii in the group-V, N is more interesting than others.…”

The photoluminescence characterization of the N-doped ZnO films produced by wet chemical deposition

“…But the result of a first-principle calculation predicts that the N element is the best candidate for producing the p-type ZnO due to small strain effects and shallow acceptor levels of substitution of N for O [2,3]. So a lot of methods have been used to prepare p-type nitrogen-doped ZnO films, such as molecular beam epitaxy, radio-frequency magnetron sputtering, ion-implantation, pulsed-laser deposition and so on [10][11][12][13][14][15]. However, a reproducible low resistance and high mobility p-type ZnO film has not been successfully obtained.…”