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Advanced nitrogen sources electronic semi-conductor thin film fabrication

Exploitable results

The main objective of this project was to develop MBE (Molecular Beam Epitaxy) technology for the low temperature growth of element III nitrides. We have developed an ECR (electron cyclotron resonance) plasma source for N2. It is operated at 2.45 GHz. The source can be used as an ion source or as an atomic source. Different configuration, materials are proposed depending on applications, so that this source is very versatile. Main qualities of the plasma are uniformity and stability. Finally, this source has been demonstrated to behave well with other gases, including oxygen, hydrogen, argon. We have developed an ammonia high temperature injector. Using this injector at room or medium (<600 C) temperatures with ammonia, we obtain excellent nitride properties with a good uniformity on 2" wafers and with a GaN growth rate of 1µm/h. At medium temperature, there is no significant influence of ammonia pre-cracking on both the growth rate and the material quality. At very high temperature (700 C), the growth rate decreases due to the recombination of pre-cracked ammonia into N2 and H2. These results indicate that the high-temperature operation capability of the injector is not useful for the growth process itself. However, it is of key importance that the injector can heated at high temperature and thus correctly outgased and cleaned. The third product developed in the frame of « ANISET » is a gallium nitride dedicated reactor. It is a 2 inch research & development reactor. It provides a cost effective approach for MBE of nitrides. Emphasis was put on the position of sources so as to increase the N incorporation and improve the uniformity of thickness, doping and alloy composition of the layers. This reactor can also be used for growing other materials. Finally, we grew GaN layers, studied the n and p doping and InGaN/GaN, GaN/AlGaN quantum wells. Most of the results have given rise to publications, showing that state of the art material could be grown using the tools developed in the frame of ANISET. Let us just mention that a GaN layer with an exciton line as narrow as 3.5 meV (PL at 10K) was grown on GaN/sapphire, GaN was grown on Si with a record 5 meV PL line (D X at 10 K), GaN/AlGaN and InGaN/GaN LEDs were obtained on sapphire and on Si. These results prove that device quality material can be obtained using the tools developed within the consortium, after a process optimization is done by the customer according to its own specifications. These results also show that GaN can be grown with an ammonia consumption much lower than that needed for the MOCVD process, with an obvious economical and environmental positive impact.