电子回旋共振等离子体特性及其对生长氮化镓晶膜的影响

PROPERTIES OF ELECTRON CYCLOTRON RESONANCE PLASMAS AND THEIR INFLUENCE ON THE DEPOSITION OF GaN FILMS

为了解并优化在电子回旋共振等离子体辅助化学汽相沉积ＧａＮ晶膜的工艺研究中的等离子体特性，利用朗缪尔探针及法拉第筒系统地测量了离子密度（Ｎｉ）、等离子体势（Ｖｐ）、电子温度（Ｔｅ）及离子流强（Ｊｉ）等多个等离子体参量随微波功率（Ｐｗ）及沉膜室气压（ｐ）变化的关系．给出了在Ｐｗ＝８５０Ｗ，ｐ＝０２２Ｐａ时，上述等离子体参量的轴向及径向分布．ＧａＮ晶膜的生长速率、电学及晶体学性能与生长条件密切相关．提高生长时的离子密度能提高ＧａＮ晶膜的氮镓比和本底电子浓度．在优化的等离子体环境下，ＧａＮ晶膜的生长速率达到０９μｍ／ｈ，其双晶Ｘ射线衍射回摆曲线的半高宽度为１６′

Abstract Langmuir probes and Faraday cups have been used to characterize electron cyclotron resonance plasmas which have been used in the depositions of GaN films on the substrate of (0001)α Al 2O 3.These plasmas were generated with microwave power( P w) from 300W to 1100W at pressures( p ) range from 0 8Pa to 0 05Pa using N 2 as the plasma source.The relationship between the plasma parameter,such as ion density( N i),electron temperature( T e),plasma potential( V p) and ion current density( J i),and system parameters,such as p W and p,is given.And the axial and radial distributions of T e, N i, V p and J i are presented.The growth rate and the quality of the GaN film strongly depend on the growth condition.The higher the plasma density,the higher the N/Ga ratio of GaN film.When the microwave power was 850W and gas pressure was 0.22Pa,the plasma near the substrate was characterized by a T e near 1.4eV and plasma density near 2.0×10 11 cm -3 ,and the growth rate of GaN was as high as 0.9μm/h.The full width at half maximum of double crystal X ray diffraction rocking curve is 16 arcmin.