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

A kind of p-ZnO film and preparation method thereof

Technical field

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

Background technique

Since there are many intrinsic donor defects in ZnO, such as interstitial zinc Zn _i and oxygen vacancy V ₀ , their energy levels are located at the bottom of the conduction band at 0.05eV and 0.3eV, respectively, which have a highly self-compensating effect on the acceptor. Therefore, it is difficult to realize the p-type transformation of ZnO, and the acceptor energy level of ZnO is generally very deep (except N), the holes are not easy to be thermally excited into the valence band, and the solid solubility of acceptor doping is also very low. Controllable and stable p-type doping has always been an important topic in ZnO research. At present, there are four main channels for p-type doping reported in the literature: 1. N doping 2. Ga, N co-doping 3. As doping 4. P doping. The latter two acceptor energy levels are relatively deep, the doping effect is not ideal, and both As and P are poisonous. In the first type, the active N source generally comes from NH ₃ , N ₂ or N ₂ O, but when N atoms replace O atoms, the Madelung energy is increased, which causes the localization of the N energy level, and the N energy level is deeper. The doping effect is not very ideal. The second type of donor (Ga) and acceptor (N) co-doping technology results in poor uniformity of ZnO surface particles, and the use of a higher-priced Ga source, usually using (MBE) molecular beam epitaxy process, expensive equipment , the production cost is high.

Contents of Invention

The purpose of the present invention is to provide a p-ZnO thin film and its preparation method.

The p-ZnO thin film of the present invention is a p-ZnO thin film co-doped with N as the acceptor and Al as the donor, and the doping concentration is 1.8×10 ¹⁵ cm ^-3 -4.5×10 ¹⁸ cm ^-3 .

The preparation method of the p-ZnO thin film of the present invention is to use the magnetron sputtering method, firstly clean the substrate surface and then put it into the reaction chamber of the DC reactive magnetron sputtering device, and the vacuum degree of the reaction chamber is pumped to 1×10 ^-3 Pa, then heat the substrate, the substrate temperature is 400-600 ° C, with N-containing gas (above 99.99%) and O ₂ or N-containing gas and Ar (above 99.99%) as the sputtering gas, the two gases are separated by The gas flow meter controls the buffer chamber of the input device. After the buffer chamber is fully mixed, it is introduced into the vacuum reaction chamber. Under the pressure of 3-5Pa, Zn _x Al _1-x is used as the target material, where 1>x>0.6, for sputtering grow.

The aforementioned N-containing gas includes NH ₃ , N ₂ O, NO, and NO ₂ . The partial pressure ratio of N-containing gas and _O2 or N-containing gas and Ar and the content of Al in the target are adjusted according to the doping concentration, and the growth time is determined by the required thickness.

The advantages of the present invention are:

1) The equipment is simple, the operation is convenient, the Al raw material is abundant, and the price is low. The production cost is low.

2) The doping concentration is controllable and stable, which can be controlled by adjusting the different partial pressure ratios of the input N-containing gas and high-purity _O2 or Ar and the content of Al in the target.

3) The p-ZnO thin film of the present invention has a smooth surface, uniform grain size and preferred orientation.

Description of drawings

Fig. 1 is a schematic diagram of a DC reactive magnetron sputtering device adopted according to the method of the present invention. 1 and 2 in the figure are the inlet pipelines for N-containing gas and _O2 or Ar respectively; 3 is the flow meter; 4 is the buffer chamber; 5 is the sample holder; 6 is the heater; 7 is the vacuum gauge; 8 is the automatic pressure control instrument; 9 is 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 ways

Referring to Fig. 1, the preparation method of the p-ZnO thin film of the present invention will be further illustrated by an example. Put the substrate on the sample holder 5 in the reaction chamber after surface cleaning, and place the substrate to be deposited facing down to effectively prevent granular impurities from contaminating the substrate. The vacuum degree of the reaction chamber is evacuated to 1×10 ^-3 Pa , using a heater to heat the substrate, the substrate temperature is controlled at 550°C; the sputtering gas is NH ₃ (above 99.99%) and O ₂ (above 99.99%), and the two-way gas enters the buffer chamber 4 through the inlet pipes 1 and 2, After the buffer chamber is fully mixed, it is introduced into the vacuum chamber, and the pressure in the vacuum chamber is controlled by an automatic pressure controller 8, and the pressure is 3Pa. The partial pressure ratio of NH ₃ and O ₂ can be adjusted through the flow meter 3 according to the doping requirements. In this example, NH ₃ : O ₂ = 60:40; Zn _x Al _1-x on the S gun 9 is used as the target Sputtering growth, in this case x=0.9. Grow at a power of 60W for 25min.

The following reactions occur during growth:

Here, v and s represent gaseous state and solid state, respectively. In the ZnO film, N-Al-N replaces O to activate N, and one N-Al-N is equivalent to a vacancy, which reduces the Madelung energy and makes the N energy level shallower. Due to the small atomic radius, H will exist in the interstitial position adjacent to N, which can largely suppress the existence of interstitial Zn during the growth process and reduce the self-compensation effect.

The p-ZnO thin film of the present invention has a flat surface, uniform crystal grain size (see FIG. 2), and has a high C-axis preferred orientation (see FIG. 3).

Claims (4)

1. A p-ZnO film, characterized in that it is a p-ZnO film co-doped with N as the acceptor and Al as the donor, and the doping concentration is 1.8×10 ¹⁵ cm ^-3 -4.5×10 ¹⁸ cm ^-3 . 2. The preparation method of the p-ZnO thin film according to claim 1 is characterized in that: put into the reaction chamber of the DC reactive magnetron sputtering device after first cleaning the substrate surface, and the reaction chamber vacuum degree is pumped to 1 × 10 ^-3 Pa, then heat the substrate, the substrate temperature is 400-600 °C, use N-containing gas and _O2 or N-containing gas and Ar as the sputtering gas, and the two gases are respectively controlled by the gas flow meter to buffer the input device The chamber is introduced into the vacuum reaction chamber after being fully mixed in the buffer chamber, and under the pressure of 3-5Pa, Zn _x Al _1-x is used as the target material, where 1>x>0.6, for sputtering growth. 3. The preparation method of p-ZnO thin film according to claim 2, characterized in that the N-containing gas includes NH ₃ , N ₂ O, NO, NO ₂ . 4. The preparation method of p-ZnO thin film according to claim 2, characterized in that said substrate is sapphire or silicon.

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