Low-resistance ohmic contacts on InAlN/GaN heterostructures with MOCVD-regrown n+-InGaN and mask-free regrowth process

This paper studied the low-resistance ohmic contacts on InAlN/GaN with metal–organic chemical vapor deposition(MOCVD)regrowth technique.The 150-nm regrown n-InGaN exhibits a low sheet resistance of 31Ω/□,resulting in an extremely low contact resistance of 0.102Ω·mm between n^(+)-InGaN and InAlN/GaN channels.Mask-free regrowth process was also used to significantly improve the sheet resistance of InAlN/GaN with MOCVD regrown ohmic contacts.Then,the diffusion mechanism between n^(+)-InGaN and InAlN during regrowth process was investigated with electrical and structural characterizations,which could benefit the further process optimization.

Improved RF power performance of InAlN/GaN HEMT by optimizing rapid thermal annealing process for high-performance low-voltage terminal applications

Improved radio-frequency(RF)power performance of InAlN/GaN high electron mobility transistor(HEMT)is achieved by optimizing the rapid thermal annealing(RTA)process for high-performance low-voltage terminal applications.By optimizing the RTA temperature and time,the optimal annealing condition is found to enable low parasitic resistance and thus a high-performance device.Besides,compared with the non-optimized RTA HEMT,the optimized one demonstrates smoother ohmic metal surface morphology and better heterojunction quality including the less degraded heterojunction sheet resistance and clearer heterojunction interfaces as well as negligible material out-diffusion from the barrier to the channel and buffer.Benefiting from the lowered parasitic resistance,improved maximum output current density of 2279 mA·mm^(-1)and higher peak extrinsic transconductance of 526 mS·mm^(-1)are obtained for the optimized RTA HEMT.In addition,due to the superior heterojunction quality,the optimized HEMT shows reduced off-state leakage current of 7×10^(-3)mA·mm^(-1)and suppressed current collapse of only 4%,compared with those of 1×10^(-1)mA·mm^(-1)and 15%for the non-optimized one.At 8 GHz and V_(DS)of 6 V,a significantly improved power-added efficiency of 62%and output power density of 0.71 W·mm^(-1)are achieved for the optimized HEMT,as the result of the improvement in output current,knee voltage,off-state leakage current,and current collapse,which reveals the tremendous advantage of the optimized RTA HEMT in high-performance low-voltage terminal applications.

木质素磺酸钠改性吸附材料对酸性橙Ⅱ的吸附性能

通过静电组装作用,以木质素磺酸钠(SL)和聚二甲基二烯丙基氯化铵(PDADMAC)为原料,在常温水介质中,制备了木质素磺酸钠-聚二甲基二烯丙基氯化铵(SL-PDADMAC)吸附材料。利用紫外分光光度法(UV)测定了其对酸性橙Ⅱ染料的吸附性能,并研究了溶液的p H、接触时间对吸附性能的影响。结果表明,吸附材料对酸性橙Ⅱ的吸附动力学符合拟二级反应动力学模型,饱和吸附容量为158.73 mg/g。

A novel Si-rich SiN bilayer passivation with thin-barrier AlGaN/GaN HEMTs for high performance millimeter-wave applications

We demonstrate a novel Si-rich SiN bilayer passivation technology for AlGaN/GaN high electron mobility transistors(HEMTs)with thin-barrier to minimize surface leakage current to enhance the breakdown voltage.The bilayer SiN with 20-nm Si-rich SiN and 100-nm Si_(3)N_(4) was deposited by plasma-enhanced chemical vapor deposition(PECVD)after removing 20-nm SiO_(2)pre-deposition layer.Compared to traditional Si_(3)N_(4) passivation for thin-barrier AlGaN/GaN HEMTs,Si-rich SiN bilayer passivation can suppress the current collapse ratio from 18.54%to 8.40%.However,Si-rich bilayer passivation leads to a severer surface leakage current,so that it has a low breakdown voltage.The 20-nm SiO_(2)pre-deposition layer can protect the surface of HEMTs in fabrication process and decrease Ga–O bonds,resulting in a lower surface leakage current.In contrast to passivating Si-rich SiN directly,devices with the novel Si-rich SiN bilayer passivation increase the breakdown voltage from 29 V to 85 V.Radio frequency(RF)small-signal characteristics show that HEMTs with the novel bilayer SiN passivation leads to f_(T)/f_(max) of 68 GHz/102 GHz.At 30 GHz and V_(DS)=20 V,devices achieve a maximum P_(out) of 5.2 W/mm and a peak power-added efficiency(PAE)of 42.2%.These results indicate that HEMTs with the novel bilayer SiN passivation can have potential applications in the millimeter-wave range.

High linearity AlGaN/GaN HEMT with double-Vth coupling for millimeter-wave applications

We demonstrated an AlGaN/GaN high electron mobility transistor(HEMT)namely double-Vthcoupling HEMT(DVC-HEMT)fabricated by connecting different threshold voltage(Vth)values including the slant recess element and planar element in parallel along the gate width with N;O plasma treatment on the gate region.The comparative studies of DVC-HEMT and Fin-like HEMT fabricated on the same wafer show significantly improved linearity of transconductance(Gm)and radio frequency(RF)output signal characteristics in DVC-HEMT.The fabricated device shows the transconductance plateau larger than 7 V,which yields a flattened fT/fmax-gate bias dependence.At the operating frequency of 30 GHz,the peak power-added efficiency(PAE)of 41%accompanied by the power density(Pout)of 5.3 W/mm.Furthermore,the proposed architecture also features an exceptional linearity performance with 1-d B compression point(P1 d B)of 28 d Bm,whereas that of the Fin-like HEMT is 25.2 d Bm.The device demonstrated in this article has great potential to be a new paradigm for millimeter-wave application where high linearity is essential.