使用TEGa和TMGa为镓源MOCVD生长GaN的研究

Growth of GaN with TEGa and TMGa by MOCVD

采用自行研制的立式MOCVD生长系统 ,以TMGa、TEGa为Ga源 ,在不同的生长条件下生长GaN单晶膜。然后对样品进行室温光致发光光谱测试、范德堡霍尔测量和X射线双晶衍射测试。实验结果表明 ,缓冲层的Ga源不同对GaN单晶膜质量影响很大 ;以TEGa为Ga源生长缓冲层及外延层 ,外延层不连续 ;以TMGa为缓冲层Ga源、TEGa为外延层Ga源 ,在此得到室温载流子浓度为 4 5× 1 0 17cm-3 ,迁移率为 1 98cm2 /V·s的电学性能较好的GaN单晶膜。研究结果表明 :使用TEGa为外延层Ga源生长GaN ,能有效地抑制不期望的蓝带的出现。

The growth of unintentionally doped GaN films was performed by organometallic vapor phase epitaxy on (0001) sapphire substrates using a home made vertical reactor at atmospheric pressure.These GaN films were grown using trimethylgallium(TMGa) and triethylgallium(TEGa) as Ga precursors under different growth condition.The blue ammonia was used as N source.The mixed gases of hydrogen and nitrogen were used as the carrier gases.The sapphire substrate was heated at 1100℃ for 10 minutes before the GaN growth.Then a thin buffer layer with thickness of about 15nm was grown at 520℃ and recrystallized at 1060℃ for 6 minutes.The GaN films were grown at 1060℃ and its thickness was about 1μm.The morphorlogical ,crystalline,electrical and optical characteristics of GaN films were measured by metalloscope observation ,X ray double crystal diffraction measurement,Van der Pauw Hall method and PL spectra measurement at room temperature,respectively.The metalloscope observation results indicated that the epilayer of sample A was uncontinuous.So we inferred that the nucleation sites were not enough when using TEGa as buffer's Ga source.By analyzing the experiment results and growth condition,it is suggested that TEGa is not very suitable to be used as buffer layer's Ga precursor,but it is good precursor as the epilayer's sources in growth of GaN films.The carrier gas ratio[H 2]/[N 2]influenced the epilayer quality greatly.When using TEGa as epilayer's Ga source and TMGa as buffer's Ga source,we obtained GaN single crystal films with RT background carrier concentration of 4 5×10 17 cm -3 and the mobility of 198cm 2/V·s.The PL measurement indicated that the blue luminescence can be suppressed using TEGa as the epilayer's Ga precursor.