Font Size: a A A

Study Of Characteristics Of In(Al)GaN Heterostructure Materials And Devices

Posted on:2018-08-12Degree:MasterType:Thesis
Country:ChinaCandidate:K PangFull Text:PDF
GTID:2348330542952567Subject:Engineering
Abstract/Summary:PDF Full Text Request
In recent years,AlGaN/GaN HEMTs?heterojunction high electron mobility transistor?devices are one of the hotspots in GaN-based electronic devices.This thesis is the study carried out in this context.AlGaN/In GaN HEMTs with high output current density,excellent transconductance characteristics and high stability at high temperature have been obtained by using InGaN instead of GaN as channel layer.InAlGaN was used instead of AlGaN as barrier layer and the normally-off InAlGaN/GaN HEMTs devices have been obtained.The results of the study are as follows:1.By the use of the theory of heterojunction polarization,the In0.15Al0.43Ga0.42N/GaN heterojunction materials with compress strain have been realized by the modulation of lattice constant of In and Al alloy in AlGaN.The results show that RMS is only 0.69 nm,and there is no In precipitation.The RSM?reciprocal space mapping?results show that the barrier layer is in a fully strained state.The 2DEG?Two-dimensional electron gas?mobility is 1248.86 cm2/V·s,the 2DEG density is 9.21×1011 cm-2,and the sheet resistance is 10.04 k?/?.2.The Al0.3Ga0.7N/In0.06Ga0.94N/GaN double heterojunction materials on sapphire have been realized by the combination of MOCVD?metal organic compound chemical vapor deposition?and PMOCVD?pulsed metal organic chemical vapor deposition?.The energy band structure of AlGa N/In GaN/GaN double heterojunction is analyzed by using the one-dimensional Schrodinger equation and Poisson's equation.Simulation results show excellent effect of confinement of the InGaN channel layer and natural GaN back barrier.The results of surface morphology,crystal quality and electrical characterization show that the double heterostructure materials exhibit a clear stepped morphology with RMS?surface roughness?of 0.20 nm.The screw and edge dislocation densities are 9.37×107 cm-3 and8.33×108 cm-3.The electron mobility and 2DEG sheet density are 1613.5 cm2/V·s and1.29×1013 cm-2 at 298 K.It is showed that the degradation rate of 2DEG mobility was 14%lower than that of conventional AlGaN/GaN structures from 298 K to 573 K by high temperature tests.3.High performance AlGaN/InGaN/GaN HEMTs have been successfully fabricated.The maximum output current density and transconductance peak are 1002.40 mA/mm and140.74 mS/mm.Transconductance stability is maintained at a higher level in the larger gate voltage range.The DIBL coefficient is only 3.67 mV/V,which is much lower than that of conventional AlGaN/Ga N HEMTs.From 298 K to 523 K,the high temperature test showed that the reduction of saturation output current density and transconductance peak of the device are 10%and 8%lower than the conventional devices.DIBL coefficient decreases 30.34%less than conventional AlGaN/GaN HEMTs.In terms of AC characteristics,f T?characteristic frequency?and f MAX?maximum oscillation frequency?are9.2 GHz and 16.1 GHz with the gate length of 1?m.4.The normally-off HEMTs have been fabricated on In0.15Al0.43Ga0.42N/GaN heterojunction.The threshold voltage is+0.43 V,which means that the normally-off characteristic has been achieved.The maximum output current density and transconductance peak are 249.92 mA/mm and 104.63 mS/mm.The DIBL coefficient is11.88 mV/V.Due to the use of InAlGaN barrier layer,the breakdown voltage is 84.5 V.High temperature test showed that the breakdown voltage dropped to 60.5 V when the temperature rises from 298 K to 573 K.The current collapse effect is tested by double-pulse dynamic IV test.The output current peak decreases by only 15.71%at the quiescent point of?-6,10?.It indicates that there is few trap state with the improvement of materials and structure.
Keywords/Search Tags:Gallium Nitride, High Electron Mobility Transistor, double heterostructure, normally-off, Indium(Aluminum) Gallium Nitride
PDF Full Text Request
Related items