CN101235536A - Na-doped growth method of p-type ZnO crystal film - Google Patents

Abstract

The method for growing a p-type ZnO crystal thin film with Na doping disclosed by the present invention adopts a pulsed laser deposition method. Firstly, pure zinc oxide and sodium carbonate powder are ball-milled and mixed, then pressed into shape and sintered to obtain a Na ₂ O-doped ZnO target. material; then in the growth chamber of the pulsed laser deposition device, use Na ₂ O-doped ZnO as the target material, pure O ₂ as the growth atmosphere, control the O ₂ pressure at 15-45pa, and the laser frequency at 1-5Hz to grow on the substrate. p-type ZnO crystal thin film. The method of the invention can realize real-time doping, and the doping concentration can be controlled by adjusting the growth temperature and the molar content of Na in the target material. The p-type ZnO crystal thin film prepared by the method of the invention has good electrical properties, repeatability and stability.

Description

Na-doped growth method of p-type ZnO crystal film

technical field

The invention relates to a growth method of p-type ZnO crystal thin film, especially a method for growing p-type ZnO crystal thin film by Na doping.

Background technique

As a wide bandgap semiconductor, ZnO has its unique advantages. The energy band width at room temperature is 3.37eV, and the exciton binding energy is 60meV, which is much larger than GaN's exciton binding energy of 25meV and room temperature molecular thermal kinetic energy of 26meV. Therefore, It has great potential to realize high-power semiconductor laser devices. However, an important step towards the application of ZnO in optoelectronic devices is to realize stable p-type ZnO thin films. ZnO behaves as n-type due to various intrinsic defects, such as Zn _i , Zn _o , and unintentional doping defects, such as H _i . The doping of acceptor impurities in ZnO will increase the Madelung energy of the system and cause a strong donor compensation effect at the same time. Finding a suitable p-type ZnO doping source is the direction that international scientists have been working hard for. Internationally reported materials that can be used as p-type ZnO doping materials include group V elements: N, P, As, etc. and group I elements Li . However, in terms of theoretical calculations, group I element Na as an acceptor has a shallower acceptor energy level than group V elements and a performance closer to Zn atomic radius than Li. The PLD method has the advantages of low substrate temperature, easy control of deposition parameters, easy to keep the composition of the film consistent with the target, and good quality of the grown film. However, this method has not been used to grow Na-doped p-type ZnO films. The invention is a method for growing p-type ZnO crystal thin film by using the pulse laser deposition technology and taking the Na-doped oxide target as the laser target material.

Contents of the invention

The purpose of the present invention is to overcome the deficiency existing in p-type ZnO doping at present, and provide a method for growing p-type ZnO crystal film by Na doping.

The method for Na-doped growth p-type ZnO crystal thin film of the present invention, what adopted is the pulsed laser deposition method, and its steps are as follows:

1) Mix pure zinc oxide and sodium carbonate powders by ball milling, press them into shape, pre-sinter at 600-800°C for more than 2 hours, and then sinter at 1000-1500°C for more than 2 hours to prepare Na ₂ O-doped ZnO targets, The molar content of Na is 0.2-1.0%;

2) Clean the surface of the substrate and put it into the growth chamber of the pulsed laser deposition device. The vacuum degree of the growth chamber is evacuated to at least 10 ^-3 Pa, and then the substrate is heated so that the substrate temperature is 500-700°C to dope Na ₂ O ZnO is used as the target material, pure _O2 is used as the growth atmosphere, the _O2 pressure is controlled at 15-45pa, the laser frequency is 1-5Hz, and the growth is carried out. After growth, it is cooled in an oxygen protective atmosphere.

The aforementioned substrate can be zinc oxide, silicon, sapphire, glass or quartz. The purity of said zinc oxide is above 99.99%.

The invention can prepare p-type ZnO crystal films with different doping concentrations by adjusting the molar content and temperature of doped Na, and the growth time is determined by the required thickness.

Advantages of the present invention:

1) Real-time doping can be realized, and p-type doping can be realized simultaneously during the growth process of ZnO crystal film;

2) The doping concentration is high, because the pulsed laser deposition technology can completely copy the composition of the target material into the grown film, so as long as the dopant concentration of the prepared target material is high, a high doping concentration can be obtained;

3) The doping concentration can be controlled by adjusting the growth temperature and the molar content of Na in the target;

4) The prepared p-type film has good electrical properties, repeatability and stability.

Description of drawings

Fig. 1 is the x-ray diffraction (XRD) pattern of the p-type ZnO crystal film of Na doping;

Fig. 2 is the photoluminescence spectrum of Na-doped p-type ZnO crystal film;

Fig. 3 is the optical transmission spectrum of Na-doped p-type ZnO crystal film.

Detailed ways

The present invention is further described below in conjunction with specific examples.

Example 1

1) Take zinc oxide and sodium carbonate powder with a purity of 99.99 _% , and the molar content of Na is 0.5%. Pour the mixed powder of ZnO and _Na2CO3 into an agate ball cup, and put it on a ball mill for ball milling. The time for ball milling is four hours. There are two purposes of ball milling: the first is to mix ZnO and Na ₂ CO ₃ powders evenly to ensure the uniformity of the prepared targets. Secondly, it is to refine the ZnO and Na ₂ CO ₃ powder, so as to facilitate the subsequent molding and sintering of the ZnO and Na ₂ CO ₃ mixed powder.

After ball milling, the powder was pressed into discs with a thickness of 3 mm and a diameter of 4 cm. Then pre-sinter at 800°C for 2 hours and sinter at 1250°C for 3 hours to ensure the decomposition of Na ₂ CO ₃ .

2) Using quartz as the substrate, clean the surface of the substrate and put it into the growth chamber of the pulsed laser deposition device. The vacuum degree of the growth chamber is pumped to 5×10 ^-3 Pa, and then the substrate is heated to make the substrate temperature 600°C , using Na ₂ O-doped ZnO as the target, adjusting the distance between the substrate and the target to 5cm, using pure O ₂ as the growth atmosphere, controlling the O ₂ pressure to 45pa, the laser frequency at 5Hz, and the laser operating voltage at 27 KV for growth. , the growth time is 60min. After growth, it is cooled under an oxygen protective atmosphere to obtain a Na-doped p-type ZnO crystal thin film with a thickness of 300 nm.

The prepared Na-doped p-type ZnO crystal film has excellent electrical properties at room temperature, with a resistivity of 27.7Ωcm, a carrier concentration of 4.64×10 ¹⁷ cm ² /Vs, and a mobility of 0.76cm ^-3 . And there is no significant change in electrical performance after two months of storage.

Figure 1 shows the X-ray diffraction pattern (XRD) of the film, only the (0002) and (0004) peaks of ZnO appear, and the half maximum width is small, indicating that the film has good crystallization properties.

Fig. 2 is the photoluminescence spectrum of above-mentioned thin film, be positioned at 3.23eV very strong edge peak and weak green light peak have proved the good photoluminescent property of the prepared Na-doped thin film, lay the foundation for the further preparation of electroluminescent device Base.

Figure 3 is the optical transmission spectrum of the above film. It can be seen from the figure that the transmittance in the visible light region is as high as 90%, and there is a steep band-edge absorption edge near 380nm, showing good optical transmittance performance.

Example 2

1) Take zinc oxide and sodium carbonate powder with a purity of 99.99 _% , and the molar content of Na is 1.0%. Pour the mixed powder of ZnO and _Na2CO3 into an agate ball cup and put it on a ball mill for ball milling. The time for ball milling is four hours. After ball milling, the powder was pressed into discs with a thickness of 3 mm and a diameter of 4 cm. Then pre-sinter at 600°C for 2 hours and sinter at 1400°C for 3 hours.

2) Using glass as the substrate, clean the substrate surface and put it into the growth chamber of the pulsed laser deposition device. The vacuum degree of the growth chamber is pumped to 5×10 ^-3 Pa, and then the substrate is heated to make the substrate temperature 550°C , using _Na2O -doped ZnO as the target, adjusting the distance between the substrate and the target to 5cm, using pure _O2 as the growth atmosphere, controlling the _O2 pressure to 30pa, the laser frequency at 3Hz, and the laser working voltage at 27KV for growth. The growth time was 60min. After growth, it is cooled under an oxygen protective atmosphere to obtain a Na-doped p-type ZnO crystal thin film with a thickness of 300 nm.

The prepared Na-doped p-type ZnO crystal film has excellent electrical properties at room temperature, with a resistivity of 63.8Ωcm, a carrier concentration of 1.72×10 ¹⁷ cm ² /Vs, and a mobility of 0.57cm ^-3 . And there is no significant change in electrical performance after two months of storage.

Example 3

1) Take zinc oxide and sodium carbonate powder with a purity of 99.99 _% , and the molar content of Na is 0.2%. Pour the mixed powder of ZnO and _Na2CO3 into an agate ball cup, and put it on a ball mill for ball milling. The time of ball milling is four hours. After ball milling, the powder was pressed into discs with a thickness of 3 mm and a diameter of 4 cm. Then pre-sinter at 600°C for 2 hours and sinter at 1400°C for 3 hours.

2) Using glass as the substrate, clean the substrate surface and put it into the growth chamber of the pulsed laser deposition device. The vacuum degree of the growth chamber is pumped to 5×10 ^-3 Pa, and then the substrate is heated to make the substrate temperature 700°C , using Na ₂ O-doped ZnO as the target, adjusting the distance between the substrate and the target to 5cm, using pure O ₂ as the growth atmosphere, controlling the O ₂ pressure to 30pa, the laser frequency at 3Hz, and the laser operating voltage at 27 KV for growth. , the growth time is 60min. After growth, it is cooled under an oxygen protective atmosphere to obtain a Na-doped p-type ZnO crystal thin film with a thickness of 300 nm.

The prepared Na-doped p-type ZnO crystal film has excellent electrical properties at room temperature, with a resistivity of 49Ωcm, a carrier concentration of 1.52×10 ¹⁷ cm ² /Vs, and a mobility of 0.84cm ^-3 . And there is no significant change in electrical performance after two months of storage.

Claims (3)

1. The method for Na-doped growth p-type ZnO crystal film is characterized in that the steps are as follows: 1) Mix pure zinc oxide and sodium carbonate powders by ball milling, press them into shape, pre-sinter at 600-800°C for more than 2 hours, and then sinter at 1000-1500°C for more than 2 hours to prepare Na ₂ O-doped ZnO targets, The molar content of Na is 0.2-1.0%; 2) Clean the surface of the substrate and put it into the growth chamber of the pulsed laser deposition device. The vacuum degree of the growth chamber is evacuated to at least 10 ^-3 Pa, and then the substrate is heated so that the substrate temperature is 500-700°C to dope Na ₂ O ZnO is used as the target material, pure _O2 is used as the growth atmosphere, the _O2 pressure is controlled at 15-45pa, the laser frequency is 1-5Hz, and the growth is carried out. After growth, it is cooled in an oxygen protective atmosphere. 2. the method for Na doping growth p-type ZnO crystal film according to claim 1 is characterized in that said substrate is zinc oxide, silicon, sapphire, glass or quartz. 3. The method for growing a p-type ZnO crystal thin film by Na doping according to claim 1, characterized in that the purity of zinc oxide is more than 99.99%.

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