| Znic oxide(Zn O) is a Ⅱ-Ⅵ direct band gap semiconductor material, with a wide band gap of 3.37 e V and large exciton binding energy of 60 me V at room temperature.So Zn O possessed high excitonic emission efficiency at room temperature. Therefore,Zn O has been taken as a promising material to fabricate ultraviolet light emitting diodes and ultraviolet laser diodes. At present, ultraviolet light emitting diodes and ultraviolet laser diodes based on Ga N have been successfully fabricated and commercialized. And the research of Ga N on ultraciolet light emitting diodes had made three Japanese scientists won the Noble Prize in Physics. However, the optoelectronic application of Zn O has not been broken though. It is due to that Zn O suffers p-doping problems. Although it has a lot of research for p-Zn O doped on international for many years, but was not able to solve the questions of p-type doping effectively. The difficult in growing p-type Zn O films includes: poor thermal stability and low solubility of acceptor, self-compensated by intrinsic defects. So it decides the future of Zn O materials directly by if we Can solve the problems of p-type doped Zn O.Aim at the problem of fabricated of p-type Zn O, We proposed the way of B and N codoping to improve solid solubility of nitrogen atom and thermal stability of Zn O.And we study optical and electrical properties of B and N codoping Zn O films, the major work and results are listed as follow:We used magnetron sputtering to prepare zinc nitride, and then got zinc oxide through thermal annealing. Using radio frequency sputtering technique, in pure argon sputtering ambient and high purity N2(or high purity NH3) as a reaction gas, to fabricate the Zn3N2. Discussing the influence of the crystallization Zn3N2 film quality on substrate temperature, gas flow ratio, and the sputtering power. We found Zn3N2 film crystallization quality was better when the substrate temperature is 200 °C,sputtering gas and reaction gas flow ratio is 1:1, sputtering power is 100 W. Zn3N2 fabricated under NH3 is annealed from 300 °C-900 °C. By spectrophotometer testing the transmission spectra of samples above, we study the change of the optical band gap.The result shows that the optical band gap of Zn3N2 is between 1.3 e V ~2.0 e V. The optical band gap of film annealed is 3.30 e V. Hall measurement shows that as-grown Zn3N2 exhibits n-type conductivity with an electron concentration to 4×1011cm-2. The as-grown Zn3N2 were annealed at different temperatures in the range of 500 °C-700 °C in the air for 1 hours. They exhibits p-type conductivity with a holeconcentration of 3×1011 cm-2 and a mobility of 0.7 cm2/Vs. When the temperature is up to 800 °C, the conductivity of Zn O is change back to n-type. This is because the N in the solid solubility of Zn O is very low, zinc-N keys will be replaced by zinc-O keys.with the increase of annealing temperature.We prepare B-doped Zn3N2 films by magnetron sputtering, and anneal B, N co-doped Zn O films in air. B doped Zn3N2 film grows at 200 °C by RF magnetron sputtering method, with zinc(Zn), boron and nitrogen(BN) as target, high-purity argon(Ar) as sputtering gas, high-purity nitrogen(N2) or ammonia(NH3) as sputtering gas. We get the sample’s transmission spectrum by spectrophotometer, which shows that the optical bandgap of the film sample made by NH3 as reaction gas is of 3.63 e V.The band gap decreases after annealing treatment. When annealed at 500°C-900 °C,the band gap of B, N co-doped Zn O films stabilizes at around 3.2e V.However, we fail to determine their Hall conductivity type because all these samples are in a high impedance state. The optical bandgap of the B-doped Zn3N2 film sample made using N2 as reaction gas stbilies at around 3.3e V after anneal. Hall measurement indicates that the sample annealed at 700 °C takes on p-type conduction property, and the hole surface density concentration is of 1.2 × 107 cm-2. |
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