Research Of MOCVD Reactor Structure With Vertical Gas Inlets

The group III nitride has widely applied prospects in light-emitting diodes,ultraviolet detectors,laser radars,and high-power electronic devices due to its wide band gap,high thermal conductivity,high electronic saturation,and high breakdown electric field.Because of the good growth controllability of film,large epitaxial layer areas,good growth uniformity,and large-scale production,metal organic chemical vapor deposition(MOCVD)has become the most popular technology in the epitaxy growth thin films of group III nitride.The performances of MOCVD reactor determine the thin film growth of high-quality group III nitride.In order to improve the MOCVD performances,the vertical MOCVD reactor was studied by computational fluid dynamics(CFD).Firstly,a numerical model of GaN deposition,including fluid flow,heat transfer,mass transfer and chemical reaction,was established based on the self-designed BDS-MOCVD reactor.Then the effects of gas inlets radius,gas inlets spacing,rotation speed,and chamber height on the MOCVD performances were studied by orthogonal experiment.The results show the sequence of parameters that influence growth rate is: chamber height > rotation speed > gas inlets spacing > gas inlets radius;the sequence for growth uniformity is: chamber height > gas inlets radius > rotation speed > gas inlets spacing.The variance analysis results indicate that the effect ratio of chamber height on the growth rate and growth uniformity is 36.267% and 74.910%,respectively.The optimal parameters for growth uniformity is the gas inlets radius of 3 mm,the gas inlets spacing of 18 mm,the rotation speed of 100 rpm,and the chamber height of 50 mm,which leads to the growth non-uniformity of 0.035 and the growth rate of 1.64 um/h.Secondly,the effects of flow rate and rotation speed on the low-chamber mode MOCVD reactor were studied.The flow stability is deteriorated,the source utilization rate is decreased from 20.75‰ to 3.94‰,the growth non-uniformity is increased from 0.0462 to 0.153 when the flow rate increases from 60 slm to 360 slm.Considering the flow stability,source utilization,and growth uniformity,the best flow rate is 120 slm.When the rotation speed increases from 50 rpm to 1050 rpm,the growth rate becomes larger,the circumferential growth uniformity becomes better,and the aggravated “pump effect” deteriorates the radial growth uniformity.When the rotation speed is 300 rpm,the substrate has a minimum growth non-uniformity of 0.0346.Finally,the effects of V/III ratio and rotation speed on the high-chamber mode MOCVD reactor were studied.When V/III increases from 10 to 175,the density difference between group III inlets and group V inlets becomes larger,resulting in the deteriorated flow stability,the increased growth non-uniformity,and the growth rate from 1.450 um/h to 2.233 um/h.At V/III = 92.5 and V/III = 175,the substrate has the lowest growth non-uniformity of 0.0513 and 0.0681 at 550 rpm,respectively.In addition,at V/III = 10,the decomposition of gallium source dominates the GaN deposition.While the pyrolysis of amino-containing adducts dominates the GaN deposition at V/III = 175.The effect of reactor height and rotational speed on the ceiling-coating is also studied.