CN1278385C - P-ZnO thin film and preparation thereof - Google Patents

Abstract

The present invention relates to a p-ZnO thin film which is a codoped p-ZnO thin film using N as acceptor doping sources and Al as donor doping sources with the doping concentration of 1.8*10 <15> cm <-3>-4.5*10<18> cm <-3>. The thin film has a preparing method that a magnetic control sputtering method is used, and Zn<x>Al<1-x> is used as target materials (1>x>0.6); the doping concentration can be controlled through regulating the different differential pressure ratios of N gas and high purified O2 or Ar to be introduced as well as regulating the content of Al of the target materials, and has good controllability and stability. The present invention has the advantages of simple device, convenient operation, rich raw material of Al, cheap price and low manufacturing cost. The N-Al-Np type ZnO thin film generated by codoping donors and acceptors of the present invention has the advantages of smooth surface, uniform grain size and preferred orientation.

Description

P-ZnO film and preparation method thereof

Technical Field

The invention relates to a semiconductor device, in particular to a p-ZnO film and a preparation method thereof.

Background

Due to the existence of many intrinsic donor defects in ZnO, such as interstitial Zn_iAnd oxygen vacancy V₀The energy levels of the self-compensating material are respectively located at the conduction band bottom 0.05eV and 0.3eV, and the self-compensating material has a high self-compensating effect on an acceptor. Therefore, it is difficult to realize p-type conversion of ZnO, and the acceptor level of ZnO is generally deep (except for N), holes are not easily thermally excited into the valence band, and the solid solubility of acceptor doping is also low. Controllable and stable p-type doping is always an important subject in ZnO research. The literature reports that there are mainly four channels for p-type doping: 1. doping N2, doping Ga and N together 3, doping As 4 and doping P. The latter two acceptor levels are both relatively deep, the doping effect is not ideal,and both As and P are toxic. The first medium active N source is generally derived from NH₃、N₂Or N₂O, but when the N atom replaces the O atom, the Madelung energy is improved, so that the N level is localized, the N level is deeper, and the doping effect is not ideal. The ZnO surface particles obtained by the second donor (Ga) and acceptor (N) co-doping technology have poor uniformity, a Ga source with higher price is required, and an (MBE) molecular beam epitaxy process is generally adopted, so that the equipment is expensive and the manufacturing cost is high.

Disclosure of Invention

The invention aims to provide a p-ZnO film and a preparation method thereof.

The p-ZnO film is a p-ZnO film codoped by taking N as an acceptor and Al as a donor, and the doping concentration is 1.8 multiplied by 10¹⁵cm^-3-4.5×10¹⁸cm^-3。

The preparation method of the p-ZnO film utilizes a magnetron sputtering method, firstly cleans the surface of the substrate, then puts the substrate into a reaction chamber of a direct current reaction magnetron sputtering device, and pumps the vacuum degree of the reaction chamber to 1 multiplied by 10^-3Pa, then heating the substrate at 400-600 deg.C to obtain N-containing gas (above 99.99%) and O₂Or using N-containing gas and Ar (more than 99.99%) as sputtering gas, respectively controlling buffer chamber of input device by gas flowmeter, fully mixing them, introducing them into vacuum reaction chamber, and making them undergo the process of reaction under the condition of 3-5Pa pressure and Zn_xAl_1-xIs used as a target material, wherein 1 is more than x is more than 0.6, and sputtering growth is carried out.

The N-containing gas comprises NH₃、N₂O、NO、NO₂. N-containing gas and O₂Or the partial pressure ratio of the N-containing gas and Ar and the content of Al in the target material are adjusted according to the doping concentration, and the growth time is determined by the required thickness.

The invention has the advantages that:

1) simple equipment, convenient operation, rich Al raw material and low price. The manufacturing cost is low.

2) The doping concentration is controllable and stable, and the N-containing gas and the high-purity O can be adjusted and input₂Or ArDifferent partial pressure ratios and the content of Al in the target material.

3) The p-ZnO film has the advantages of flat surface, uniform grain size and preferred orientation.

Drawings

FIG. 1 is a schematic view of a DC reactive magnetron sputtering apparatus used in the method according to the present invention. In the figure, 1 and 2 are respectively N-containing gas and O₂Or an air inlet line for Ar; 3 is a flowmeter; 4 is aA buffer chamber; 5 is a sample holder; 6 is a heater; 7 is a vacuum gauge; 8 is an automatic pressure controller; 9 is an S gun

FIG. 2 is an AFM (atomic force microscope) photograph of the surface of a p-ZnO thin film.

FIG. 3 is an XRD (X-ray diffraction) pattern of a p-ZnO thin film deposited on sapphire.

Detailed Description

The method of making the p-ZnO thin film of the present invention is further illustrated by way of example with reference to FIG. 1. Firstly, the substrate is cleaned and placed on the sample holder 5 of the reaction chamber, the surface to be deposited of the substrate is placed downwards, so that the contamination of granular impurities to the substrate can be effectively prevented, and the vacuum degree of the reaction chamber is pumped to 1 x 10^-3Pa, heating the substrate by using a heater, and controlling the temperature of the substrate to be 550 ℃; the sputtering gas being NH₃(99.99% or more) and O₂(more than 99.99 percent), the two paths of gas enter a buffer chamber 4 through gas inlet pipes 1 and 2, the gas is fully mixed in the buffer chamber and then is introduced into a vacuum chamber, and the pressure in the vacuum chamber is controlled by an automatic pressure controller 8 and is 3 Pa. NH (NH)₃And O₂The partial pressure ratio can be adjusted by means of a flow meter 3, in this case NH, according to the doping requirements₃∶O₂60: 40; with Zn on S gun 9_xAl_1-xThe target was sputter grown, in this case x is 0.9. The growth was carried out at a power of 60W for 25 min.

The following reactions occur during growth:

here, v and s represent a gas state and a solid state, respectively. In the ZnO film, N-Al-N substitutes for O to activate N, and one N-Al-N corresponds to one vacancy, so that Madelung can be lowered and the N level is shallower. And H can exist in a gap position adjacent to N due to smaller atomic radius, so that the existence of a gap Zn in the growth process can be greatly inhibited, and the self-compensation effect is reduced.

The p-ZnOfilm has a flat surface, uniform grain size (see figure 2) and high C-axis preferred orientation (see figure 3).

Claims (4)

1. The p-ZnO film is characterized in that the p-ZnO film is codoped by taking N as an acceptor and Al as a donor, and the doping concentration is 1.8 multiplied by 10¹⁵cm^-3-4.5×10¹⁸cm^-3。

2. The method for preparing a p-ZnO film as defined in claim 1, wherein: firstly, the surface of the substrate is cleaned and then put into a reaction chamber of a DC reaction magnetron sputtering device, and the vacuum degree of the reaction chamber is pumped to 1 multiplied by 10^-3Pa, then heating the substrate at 400-600 deg.C to obtain N-containing gas and O₂Or N-containing gas and Ar as sputtering gas, respectively controlling the buffer chamber of the input device by a gas flowmeter, fully mixing in the buffer chamber, introducing into a vacuum reaction chamber, and reacting under 3-5Pa pressure with Zn_xAl_1-xIs used as a target material, wherein 1 is more than x is more than 0.6, and sputtering growth is carried out.

3. The method for preparing p-ZnO film according to claim 2, wherein the N-containing gas comprises NH₃、N₂O、NO、NO₂。

4. The method for preparing p-ZnO film according to claim 2, wherein the substrate is sapphire or silicon.

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