磁控溅射工作压强对β-Ga2O3薄膜特性的影响

作为新兴的第三代半导体材料,β-Ga₂O₃高质量薄膜是制备高效Ga₂O₃基器件的基础,β-Ga₂O₃薄膜的制备、表征及光电特性的研究具有深刻的意义。通过分析研究磁控溅射工作压强变化对薄膜性能和形貌的影响,为制备更高质量的薄膜提供了一种新的方法。基于射频磁控溅射方法,在单晶c面蓝宝石(Al₂O₃)衬底上沉积生长Ga₂O₃薄膜,并进行900℃、90min的氮气退火处理,以得到β-Ga₂O₃薄膜。沉积过程不改变其他实验参数,仅改变工作压强,研究工作压强对β-Ga₂O₃薄膜特性的影响。X射线衍射仪(XRD)和原子力显微镜(AFM)表征结果显示,β-Ga₂O₃薄膜具有不同取向的衍射峰,沿着■晶向择优生长,薄膜呈多晶状态。适当增大工作压强可使β-Ga<...     

Si/Mg/Fe掺杂β-Ga2O3单晶拉曼光谱表征及分析

β-Ga₂O₃单晶材料由于其优异的性能得到了广泛关注,但是对于其掺杂、能级、电学性能等方面的研究仍然比较欠缺。采用导模法分别制备了非故意掺杂β-Ga₂O₃单晶和Si/Mg/Fe掺杂的β-Ga₂O₃单晶,对样品进行了拉曼光谱测试和电学性能测试,研究不同掺杂元素对拉曼光谱的影响。对β-Ga₂O₃单晶的声子谱进行计算,并通过拉曼光谱测试进行了验证,对掺杂元素的取代位置进行了分析。结果表明,掺杂元素会对拉曼峰强度产生显著影响,Si、Mg、Fe均倾向于取代Ga_ⅡO₆八面体中心的Ga_Ⅱ原子。根据电学性能测试结果,Si掺杂会使β-Ga₂O₃单晶呈n型导电,Mg或Fe掺杂会使β-Ga₂O₃单晶呈半绝缘态。     

磁控溅射氧氩体积流量比对β-Ga2O3薄膜的影响

利用射频磁控溅射在c面单晶蓝宝石(Al₂O₃)衬底上制备Ga₂O₃薄膜,研究了溅射过程中通入氧气与氩气的体积流量比对经过异位高温后退火处理得到的β-Ga₂O₃薄膜特性的影响。利用X射线衍射仪(XRD)和原子力显微镜(AFM)对薄膜进行表征,结果表明β-Ga₂O₃薄膜沿着■晶面择优生长,具备较好的单一取向性。在氧氩体积流量比约为1∶20时,薄膜的结晶性能相对较好、表面晶粒分布较均匀、均方根粗糙度较小、晶粒尺寸较大。此外,吸收光谱表征结果表明,不同氧氩体积流量比下制备得到的β-Ga₂O₃薄膜的带隙变化范围为4.53～4.64 eV,在较低氧氩体积流量比下制备的β-Ga₂O₃薄膜表现出较优的光学性质,在波长200～300 nm内具有较好的吸收特性,表现出良好的深紫外光学特性。     

导模法生长的β-Ga2O3单晶的位错腐蚀坑显露面

β-Ga₂O₃单晶作为高压大功率器件的衬底,其位错密度直接影响器件的漏电特性,位错腐蚀坑显露面与外延生长密切相关。β-Ga₂O₃单晶属于单斜晶系,对称性低,研究不同晶面位错腐蚀坑的形状与显露面难度较高。对采用导模(EFG)法生长的(001)、■和(010)面β-Ga₂O₃晶片进行腐蚀,采用扫描电子显微镜(SEM)观测腐蚀坑形貌,采用共聚焦激光扫描显微镜对显露面与表面晶面之间的夹角进行表征,根据测试结果可推算出腐蚀坑显露面晶面指数,为衬底和外延生长提供重要的参考依据。     

增强型β-Ga2O3/4H-SiC异质结VDMOS的设计与研究

由于β-Ga₂O₃材料难以形成P型掺杂，目前β-Ga₂O₃功率器件大多为无结耗尽型。为了解决β-Ga₂O₃器件难以形成增强型的问题，提出了一种具有β-Ga₂O₃/4H-SiC异质结的纵向双扩散金属-氧化物-半导体场效应晶体管(VDMOS)。添加P型4H-SiC后，利用形成的PN结的单向导通性得到了正阈值电压，实现了增强型器件。使用Sentaurus TCAD仿真软件模拟了器件结构并研究了其电学特性，通过调节SiC厚度、SiC沟道浓度、外延层厚度和外延层浓度四个重要结构参数，对器件的功率品质因数进行优化设计。优化后的器件具有1.62 V的正阈值电压、39.29 mS/mm的跨导以及5.47 mΩ·cm²的比导通电阻。最重要的是器件的关态击穿电压达到了1838 V,功率品质因数高达617 MW/cm²。结果表明，该β-Ga₂O₃/...     

Homoepitaxial growth of (100) Si-doped β-Ga2O3 films via MOCVD

Homoepitaxial growth of Si-doped β-Ga₂O₃ films on semi-insulating(100) β-Ga₂O₃ substrates by metalorganic chemical vapor deposition(MOCVD) is studied in this work. By appropriately optimizing the growth conditions, an increasing diffusion length of Ga adatoms is realized, suppressing 3D island growth patterns prevalent in(100) β-Ga₂O₃ films and optimizing the surface morphology with [010] oriented stripe features. The slightly Si-...     

CVD法制备的高结晶质量二维β-Ga2O3薄膜性质研究

为了能够得到高质量的薄膜,降低实验成本,通过化学气相沉积(CVD)方法以GaTe粉作为Ga源在云母衬底上合成了β-Ga₂O₃薄膜。通过改变生长温度、载气和生长时间得到高结晶质量的β-Ga₂O₃薄膜,并通过X射线衍射(XRD)和拉曼光谱进行证实。XRD结果显示,薄膜的最佳生长温度为750℃。对比不同载气下合成的β-Ga₂O₃薄膜可知,Ar气是生长薄膜材料的最佳环境。为了实现高结晶质量的β-Ga₂O₃薄膜,在Ar气环境下改变薄膜的生长时间,XRD结果发现,生长时间20 min的薄膜具有高结晶质量。最后,将其转移到300 nm厚氧化层的Si/SiO₂衬底上,并通过原子力显微镜测试,证实了16 nm厚的二维Ga₂O₃薄膜。     

氧分压对脉冲激光沉积β-Ga2O3-δ薄膜光学性能的影响

在不同氧分压下,用脉冲激光沉积法在c-蓝宝石衬底上制备了高质量β-Ga₂O_3?δ薄膜。通过X-射线衍射、远红外反射光谱、X-射线光电子能谱和紫外-可见-近红外透射光谱系统地研究了β-Ga₂O_3?δ薄膜的晶格结构、化学计量比和光学性质。X-射线衍射分析表明,所有沉积的薄膜以(-201)晶向方向生长。透射光谱显示薄膜在255 nm以上的紫外-可见-近红外波段具有80%以上的高透明度,同时在255 nm附近有一个陡峭的吸收边。此外,利用Tauc-Lorentz(TL)色散函数模型和Tauc公式,我们提取了β-Ga₂O_3?δ薄膜的光学常数和光学直接带隙。更进一步,我们通过理论计算解释了氧气分压对β-Ga₂O_3?δ薄膜光学性质的影响。     

亚稳相Ga2O3异质外延的研究进展

作为一种新兴的超宽禁带半导体材料,氧化镓(Ga₂O₃)被认为是下一代高功率电力电子器件领域的战略性先进电子材料。相较于热稳定的β-Ga₂O₃,亚稳相Ga₂O₃表现出更为新颖的物理性质,逐渐受到关注。通过异质外延生长高质量的亚稳相Ga₂O₃单晶薄膜是实现亚稳相Ga₂O₃基功率电子、微波射频和深紫外光电信息感知器件的重要前提。重点阐述了亚稳相Ga₂O₃的晶体结构、电子能带结构以及相关物理性质,总结了近年来亚稳相Ga₂O₃异质外延和能带工程的研究进展,并对未来亚稳相Ga₂O₃材料和器件的发展趋势进行了展望。     

GaAs衬底上β-Ga2O3纳米点阵薄膜的MOCVD制备

将热氧化与MOCVD工艺相结合,总结了一种在本征GaAs衬底上进行β-Ga₂O₃纳米点阵薄膜制备的工艺,该工艺不涉及金属催化剂与复杂刻蚀,工艺更为简单。使用扫描电子显微镜对所制备薄膜的形貌特征进行了表征与分析,发现所制备的纳米点阵薄膜呈现五方的柱状结构。对所制备样品进行了X射线衍射、拉曼振动、光致发光谱的测试,结果表明薄膜的晶体质量随着MOCVD生长温度与Ⅵ/Ⅲ比的提高而得到优化。使用有限元法（FEM）仿真验证了β-Ga₂O₃纳米点阵薄膜制备的高陷光特点。     

2.83-kV double-layered NiO/β-Ga2O3 vertical p-n heterojunction diode with a power figure-of-merit of 5.98 GW/cm2

This work demonstrates high-performance NiO/β-Ga₂O₃ vertical heterojunction diodes(HJDs) with double-layer junction termination extension(DL-JTE) consisting of two p-typed NiO layers with varied lengths. The bottom 60-nm p-NiO layer fully covers the β-Ga₂O₃ wafer, while the geometry of the upper 60-nm p-NiO layer is 10 μm larger than the square anode electrode. Compared with a single-layer JTE, the electric field concentration is inhibited by double-la...     

超宽禁带半导体α-Ga2O3肖特基二极管仿真研究

氧化镓(Ga₂O₃)作为一种新型的超宽禁带半导体材料,与目前常用的半导体材料SiC和GaN相比,具有更大的禁带宽度、更高的击穿场强等优良特性。设计了一种基于α-Ga₂O₃的垂直型肖特基二极管(SBD),采用场板终端结构降低阳极边缘电场强度,研究了不同绝缘材料下阳极附近的电场分布,并探讨了场板结构与长度对其击穿特性的影响。仿真结果表明,在选取HfO₂作为α-Ga₂O₃垂直型SBD场板结构的绝缘材料时,场板结构可以增大该器件的反向击穿电压,最大反向击穿电压可达约1 100 V,对于现实中制备α-Ga₂O₃ SBD具有非常重要的参考意义。     

Two-step growth of β-Ga2O3 on c-plane sapphire using MOCVD for solar-blind photodetector

In this work,a two-step metal organic chemical vapor deposition(MOCVD) method was applied for growing β-Ga₂O₃ film on c-plane sapphire.Optimized buffer layer growth temperature(T_B) was found at 700℃ and the β-Ga₂O₃ film with full width at half maximum(FWHM) of 0.66° was achieved.A metal-semiconductor-metal(MSM) solar-blind photodetector(PD)was fabricated based on the β-Ga₂O₃ film.Ultrahigh responsivity of 1422 A/W@254 n...     

阳极刻蚀提升Ga2O3肖特基势垒二极管击穿特性

提出了一种采用阳极刻蚀提升Ga₂O₃肖特基势垒二极管(SBD)击穿特性的新方法。基于氢化物气相外延(HVPE)法生长的Ga₂O₃材料制备了Ga₂O₃纵向SBD。在完成阳极制备后，对阳极以外的Ga₂O₃漂移区进行了不同深度的刻蚀，刻蚀完成后，在器件表面生长了SiO₂介质层，随后制备了场板结构。测试结果显示，刻蚀后器件的比导通电阻小幅上升，而反向击穿电压均大幅提升。刻蚀深度为300 nm的β-Ga₂O₃ SBD具有最优特性，其比导通电阻(R_{on, sp})为2.5 mΩ·cm²,击穿电压(V_br)为1 410 V,功率品质因子(FOM)为795 MW/cm²。该研究为高性能Ga₂O₃ SBD的制备提供了一种新方法。     

Large-area β-Ga2O3 Schottky barrier diode and its application in DC–DC converters

We demonstrate superb large-area vertical β-Ga₂O₃ SBDs with a Schottky contact area of 1 × 1 mm² and obtain a high-efficiency DC–DC converter based on the device. The β-Ga₂O₃ SBD can obtain a forward current of 8 A with a forward voltage of 5 V, and has a reverse breakdown voltage of 612 V. The forward turn-on voltage(VF) and the on-resistance(Ron) are 1.17 V and 0.46 Ω, respectively. The conversion efficiency of the β-Ga₂O_3<...     

Exploring heteroepitaxial growth and electrical properties of α-Ga2O3 films on differently oriented sapphire substrates

This study explores the epitaxial relationship and electrical properties of α-Ga₂O₃ thin films deposited on a-plane, mplane, and r-plane sapphire substrates. We characterize the thin films by X-ray diffraction and Raman spectroscopy, and elucidate thin film epitaxial relationships with the underlying sapphire substrates. The oxygen vacancy concentration of α-Ga₂O₃ thin films on m-plane and r-plane sapphire substrates are higher than α-Ga₂O     

Electronic structure and optical properties of F-doped β-Ga2O3 from first principles calculations

The effects of F-doping concentration on geometric structure, electronic structure and optical property of β-Ga₂O₃ were investigated. All F-doped β-Ga₂O₃ with different concentrations are easy to be formed under Ga-rich conditions, the stability and lattice parameters increase with the F-doping concentration. F-doped β-Ga₂O₃ materials display characteristics of the n-type semiconductor, occupied states contributed from Ga 4s, Ga 4p and O 2p states in the conduction band increase with an increase in F-doping concentration. The increase of F concentration leads to the narrowing of the band gap and the broadening of the occupied states. F-doped β-Ga₂O₃ exhibits the sharp band edge absorption and a broad absorption band. Absorption edges are blue-shifted, and the intensity of broad band absorption has been enhanced with respect to the fluorine content. The broad band absorption is ascribed to the intra-band transitions from occupied states to empty states in the conduction band.     

High-speed performance self-powered short wave ultraviolet radiation detectors based on κ(ε)-Ga2O3

High-speed solar-blind short wavelength ultraviolet radiation detectors based on κ(ε)-Ga₂O₃ layers with Pt contacts were demonstrated and their properties were studied in detail.The κ(ε)-Ga₂O₃ layers were deposited by the halide vapor phase epitaxy on patterned GaN templates with sapphire substrates.The spectral dependencies of the photoelectric properties of structures were analyzed in the wavelength interval 200-370 nm.The maximum photo to dark curre...     

Recent advances in NiO/Ga2O3 heterojunctions for power electronics

Beta gallium oxide(β-Ga₂O₃) has attracted significant attention for applications in power electronics due to its ultrawide bandgap of ～ 4.8 eV and the large critical electric field of 8 MV/cm. These properties yield a high Baliga’s figures of merit(BFOM) of more than 3000. Though β-Ga₂O₃ possesses superior material properties, the lack of p-type doping is the main obstacle that hinders the development of β-Ga₂O₃-based power device...     

A large-area multi-finger β-Ga2O3 MOSFET and its self-heating effect

The self-heating effect severely limits device performance and reliability. Although some studies have revealed the heat distribution of β-Ga₂O₃ MOSFETs under biases, those devices all have small areas and have difficulty reflecting practical conditions. This work demonstrated a multi-finger β-Ga₂O₃ MOSFET with a maximum drain current of 0.5 A. Electrical characteristics were measured, and the heat dissipation of the device was investigated through inf...