A TEM Study of InGaN Layers and Quantum Wells Grown by MOCVD

摘要

We present an electron microscopy investigation of two series of InGaN layers grown respectively by AP-MOCVD and LP-MOCVD. For low pressure MOCVD layers, we analysed a nominal 17% In 200 nm thick layer and another sample made of three 2.4 nm nominal thickness quantum wells. For the thick layer, the EDS In composition is close to 13% instead of the nominal 17%. A close examination shows that nanometric InN precipitates, in epitaxial relationship, are present at the layer surface. In the quantum well sample, it is noticed that the QW average thickness is uniform, however, the contrast change indicates that the strain distribution is not constant which means that the indium composition fluctuates in nanometric areas. In a thick (>1 #mu#m) layer grown by AP-MOCVD, the ternary layer has undergone unstable growth. At least two steps have taken place, first, a thin ternary layer, whose In composition is less than 20%, then the growth has been disrupted.