| With the rapid development of ultra wide bandgap semiconductors,β-Ga2O3 has attracted the attention of scholars due to its excellent material properties.β-Ga2O3 has greater Johnson and Baliga figure of merit than SiC and GaN,indicating its great potential for application in the high-frequency and big-power range.AlN/β-Ga2O3 heterostructure has two-dimensional electron gas characteristics,which can be used to further develop AlN/β-Ga2O3 HEMT device.At present,the research on AlN/β-Ga2O3 HEMT devices is in its infancy.Therefore,this article uses numerical simulation methods to carry out the research on AlN/β-Ga2O3 HEMT mechanism analysis,structural parameter optimization,electrical characteristic simulation,and the influence of self-heating effect on device characteristics of AlN/β-Ga2O3 HEMT devices.The main research content and results are as follows:1.The polarization effect of AlN/β-Ga2O3 heterojunction was studied.Research shows that,the piezo polarization density direction of AlN in the AlN/β-Ga2O3 heterostructure is from N plane to Al plane,and the intensity of piezo polarization density is 0.046 C/m2.The piezo polarization density weakens the spontaneous polarization,and the final total polarization is from Al plane to N plane,and the total polarization intensity is-0.044 C/m2.The total polarized positive charge density at the AlN/β-Ga2O3 interface is 2.75 × 1013 cm-2.2.By studying the influence of structural parameters on the DC and frequency characteristics of the device,optimized structural parameters were obtained.When the thickness of the AlN barrier layer increases from 10nm to 25 nm,the decrease in gate capacitance is the main reason for the increase in cutoff frequency and maximum oscillation frequency,while the decrease in transconductance has a smaller impact.Gate length from 0.9 μm shorten to 0.1 μm,both the increase in transconductance and the decrease in gate capacitance increase the cutoff frequency and maximum oscillation frequency,but the gate length is shortened to 0.1 μm,the gate length frequency product significantly decreases and the device exhibits short channel effects.The distance between gate and drain ranges from 1.7 μm increased to 2.7 μm,the transconductance and drain saturation current significantly increase,the cutoff frequency decreases,and the maximum oscillation frequency first decreases and then increases.When the Schottky gate metal work function increases from 5.15 eV to 5.65 eV,the drain saturation current increases,while the transconductance,cutoff frequency,and maximum oscillation frequency remain basically unchanged.After structural optimization,the AlN barrier layer thickness of the device is 10nm,the gate length is 0.3 μm,the gate drain spacing is 2.7 μm,the transconductance of the device is 410 mS/mm,the drain saturation current is 1.2 A/mm,and the cutoff frequency and maximum oscillation frequency are 45 GHz and 88 GHz,respectively.3.The temperature characteristics of devices with or without self-heating effects were studied,and the reasons for device performance degradation were analyzed.When the temperature increases from 300 K to 500 K,the mobility decreases from 146 cm2·V-1·s-1 to 82 cm2·V-1·s-1,and the transconductance,drain saturation current,and cutoff frequency decrease by 49%,53%,and 49%,respectively.The decrease in mobility caused by temperature rise is the main factor leading to the degradation of device characteristics.At the same time,research has found that the self-heating effect leads to negative differential resistance in the output characteristics of the device at ambient temperatures of 300 K,400 K,and 500 K,respectively.As the temperature increases,the negative differential resistance phenomenon becomes weaker,with the transconductance and cut-off frequency of the device decreasing by 58%and 33%at room temperature,respectively.The degradation of device DC and frequency characteristics is significant. |
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