MOCVD生长的p型GaN薄膜中Mg掺杂的优化与分析

通过优化Mg流晕增强了MoCVD生长的GaN薄膜的p型电导并改善了晶体质量.Hall测量结果表明卒穴浓度首先随着Mg流量的升高而升高,达到极大值后开始降低;迁移率始终随Mg流量的升高而降低.最优的样品在室温下空穴浓度达到4.1×1017cm-3,电阻率降至1Ω·cm.考虑施主型缺陷MGaVN的自补偿作用,计算了空穴浓度随掺杂浓度变化的曲线关系.计算结果表明自补偿系数随掺杂浓度的增大而增大;空穴浓度首先随掺杂浓度的增大而增加,存受主浓度为NA≈4×1019左右时达到极大值,之后随着掺杂浓度的增大而迅速降低.XRD数据表明在实验范围内晶体缺陷密度随着掺杂浓度的降低而降低.     

MOCVD生长的GaN:Mg外延膜的光电性质

用MOCVD技术生长GaN:Mg外延膜,在550～950℃温度范围内,对样品进行热退火,并进行室温Hall、光致发光谱(PL)测试.Hall测试结果表明,850℃退火后空穴浓度达到8×1017 cm-3以上,电阻率降到0.8Ω·cm以下.室温PL谱有两个缺陷相关发光峰,位于2.8eV的蓝光峰(BL)以及3.27eV附近的紫外峰(UVL).蓝光峰对紫外峰的相对强度(BL/UVL)在550℃退火后升高,之后随着退火温度的升高(650～850℃)而下降,继续提高退火温度至950℃,BL/UVL急剧上升.空穴浓度先随着Mg掺杂浓度的增加而升高;但继续增加Mg掺杂浓度,空穴浓度反而下降.这些结果表明要实现空穴浓度达1018 cm-3,不仅要考虑H的钝化作用,还要考虑Mg受主的自补偿效应.     

MOCVD生长的GaN:Mg外延膜的光电性质

用MOCVD技术生长GaN:Mg外延膜,在550～950℃温度范围内,对样品进行热退火,并进行室温Hall、光致发光谱(PL)测试.Hall测试结果表明,850℃退火后空穴浓度达到8×1017 cm-3以上,电阻率降到0.8Ω·cm以下.室温PL谱有两个缺陷相关发光峰,位于2.8eV的蓝光峰(BL)以及3.27eV附近的紫外峰(UVL).蓝光峰对紫外峰的相对强度(BL/UVL)在550℃退火后升高,之后随着退火温度的升高(650～850℃)而下降,继续提高退火温度至950℃,BL/UVL急剧上升.空穴浓度先随着Mg掺杂浓度的增加而升高;但继续增加Mg掺杂浓度,空穴浓度反而下降.这些结果表明要实现空穴浓度达1018 cm-3,不仅要考虑H的钝化作用,还要考虑Mg受主的自补偿效应.     

InGaN:Mg薄膜的电学特性研究

利用MOCVD生长了InGaN:Mg薄膜,研究了生长温度、掺Mg量对InGaN:Mg薄膜电学特性的影响.结果表明,空穴浓度随着生长温度的降低而升高.在相同的生长温度下,空穴浓度随掺Mg量的增加,先升高后降低.通过对这两个生长条件的优化,在760℃、CP2Mg与TMGa摩尔流量之比为2.2‰时制备出了空穴浓度高达2.4×1019cm-3的p-InGaN:Mg薄膜.这对进一步提高GaN基电子器件与光电子器件的性能有重要意义.     

p型GaN的渐变δ掺杂研究

采用MOCVD技术及渐变δ-Mg掺杂方法生长了p型GaN薄膜,对样品进行了两步退火处理以对Mg进行激活.通过Hall测试发现,经过950℃下的第一次退火后,样品空穴浓度为1.64×1016cm-3,电阻率为77.9Ω·cm.经过750℃下的第二次退火后,样品的空穴浓度增大了10倍,电阻率减小为原来的1/20.分析认为,渐变δ掺杂减小了Mg的自补偿效应,两步退火提高了Mg的激活效率,从而显著提高了样品的空穴浓度和降低了电阻率.实验还发现,经过750℃下15min的第二次退火后得到的样品的空穴浓度最大,达5.13×1017cm-3.     

InGaN∶Mg薄膜的电学特性研究

利用MOCVD生长了InGaN:Mg薄膜,研究了生长温度、掺Mg量对InGaN:Mg薄膜电学特性的影响。结果表明,空穴浓度随着生长温度的降低而升高。在相同的生长温度下,空穴浓度随掺Mg量的增加,先升高后降低。通过对这两个生长条件的优化,在760°C、CP2Mg与TMGa摩尔流量之比为2.2‰时制备出了空穴浓度高达2.4×1019cm-3的p-InGaN∶Mg薄膜。这对进一步提高GaN基电子器件与光电子器件的性能有重要意义。     

镁流量对MOCVD生长的P型GaN薄膜特性的影响

利用MOCVD生长了不同Mg流量的P型GaN样品。研究了Mg流量对MOCVD生长的P型GaN薄膜的电学特性、表面形貌及晶体质量的影响。结果表明利用MOCVD制备高质量的P型GaN薄膜,Mg流量应处于一个合适的范围,Mg流量过低,薄膜的空穴浓度低,电学特性不好;Mg流量过高,则会产生大量的缺陷,晶体质量与表面形貌变差,Mg的活化率也降低,并且自补偿效应更加严重,最终使得空穴浓度降低,电学特性变差。将优化的条件应用于蓝光发光管的外延生长,并制备了器件,在20mA的注入电流下,输出功率为6.5mW,正向压降3V,反向击穿电压为20V。     

InGaN/GaN多量子阱蓝光LED的p-GaN盖层的MOCVD生长研究

利用金属有机物化学气相淀积（MOCVD）生长了InGaN／GaN多量子阱（MQW）蓝光发光二极管（LED）,研究了不同Cp2Mg流量下生长的p-GaN盖层对器件电学特性的影响。结果表明,随着Cp2Mg流量的提高,漏电流升高,并且到达一临界点会迅速恶化;正向压降则先降低,后升高。进而研究相同生长条件下生长的p-GaN薄膜的电学特性、表面形貌及晶体质量,结果表明,生长p-GaN盖层时,Cp2Mg流量过低,盖层的空穴浓度低,电学特性不好;Cp2Mg流量过高,则会产生大量的缺陷,盖层晶体质量与表面形貌变差,使得空穴浓度降低,电学特性变差。因此,生长p-GaN盖层时,为使器件的正向压降与反向漏电流均达到要求,Cp2Mg流量应精确控制。     

MOCVD生长P型GaN的掺Mg量的研究

使用MOCVD技术在Al2O3衬底上生长了GaN：Mg薄膜.通过对退火后样品的光电性能综合分析,研究了掺Mg量对生长P型GaN的影响.结果表明：要获得高空穴载流子浓度的P型GaN,Mg的掺杂量必须控制好.掺Mg量较小时,GaN：Mg单晶膜呈现N型导电,得不到P型层;掺Mg量过大时,会形成与Mg有关的深施主,由于深施主的补偿作用,得不到高空穴浓度的P型GaN.生长P型GaN的最佳Cp2Mg/TMGa之比在1/660-1/330之间     

高浓度Mg掺杂GaN的电学和退火特性研究

对高浓度Mg掺杂GaN在常规热退火和快速热退火前后的材料质量和电学特性进行了研究。X 射线衍射测量表明 ,重掺杂导致了GaN质量的下降 ,退火后略有恢复。霍尔测量表明 ,Cp2 Mg :TMGa的流量比小于 1:2 6.3时 ,退火后空穴浓度可达到 2× 10 18cm- 3;当Cp2 Mg :TM Ga的流量比为 1:2 1.9时 ,得到的高阻GaN在常规热退火和快速热退火后均只为弱 p型 ,存在明显的施主补偿现象。这被认为是重掺杂导致晶格缺陷增多 ,引入了施主能级 ,补偿了被激活的Mg原子的结果     

HV/CVD系统Si、SiGe低温掺杂外延

研究了硼烷（B2H6）掺杂锗硅外延和磷烷（PH3）掺杂硅外延的外延速率和掺杂浓度与掺杂气体流量的关系．B浓度与B2H6流量基本上成正比例关系;生长了B浓度直至1019cm-3的多层阶梯结构,各层掺杂浓度均匀,过渡区约20nm,在整个外延层,Ge组分（x=0.20）均匀而稳定．PH3掺杂外延速率随PH3流量增加而逐渐下降;P浓度在PH3流量约为1.7sccm时达到了峰值（约6×1018cm-3）．分别按PH3流量递增和递减的顺序生长了多层结构用以研究PH3掺杂Si外延的特殊性质．     

Correlation of doping concentration,charge transport of host,and lifetime of thermally activated delayed fluorescent devices

Origin of doping concentration dependence of lifetime of thermally activated delayed fluorescent (TADF) devices was examined using a TADF emitter doped in a hole transport type and a bipolar host material. Lifetime of the hole transport type host based TADF device was increased according to doping concentration of TADF emitter, while that of the bipolar host based TADF device was decreased according to doping concentration of TADF emitter. The doping concentration dependence of the lifetime could be correlated with recombination zone of the emitting layer. Broad recombination zone at high doping concentration in the hole transport type host and at low doping concentration in the bipolar host was proposed as the main contributor of the doping concentration dependence of the lifetime.     

重掺碳GaAs层的MOCVD生长及特性研究

采用 CCl4 作为碳掺杂源 ,进行了重掺碳 Ga As层的 L P- MOCVD生长 ,并且对掺杂特性进行了研究 ,研究了各生长参数对掺杂的影响。CCl4 流量是决定掺杂浓度的主要因素。减小生长温度、减小 / 比、降低生长压力 ,都能较大的提高掺杂浓度。通过改变 CCl4 流量 ,在生长温度为5 5 0～ 6 5 0℃、 / 比为 15～ 4 0 ,生长压力在 1× 10 4 ～ 4× 10 4 Pa的范围内 ,均能得到高于 2× 10 19/cm3 的掺碳 Ga As外延层 ,最高掺杂浓度为 8× 10 19/ cm3     

Enhanced efficiency in GaInP/GaAs tandem solar cells using carbon doped GaAs in tunnel junction

Carbon doping of GaAs using CBr₄ (carbon tetrabromide) in metal-organic chemical vapor deposition (MOCVD) was investigated to obtain very high and sharp doping profiles required for tunnel junction in tandem solar cells. It was found that the hole concentration increased with decreasing growth temperature and V/III ratio. Hole doping profiles versus distance from the sample surface showed that the hole concentration near the surface was very low in comparison with that far below the surface. As a post-growth treatment, CBr₄ was supplied during the cool down process and produced almost constant hole concentration of 1 × 10²⁰ cm⁻³ regardless of the depth, when CBr₄ flow rate was 9.53 μmol/min. Based on these results, solar cells were fabricated using both carbon (C) and zinc (Zn) as a p-type dopant. It was shown that C doping exhibits higher efficiency and lower series resistance than those of Zn doping in GaInP/GaAs tandem solar cells.     

p型重掺杂应变Si_(1-x)Ge_x层中少子常温和低温行为

采用解析的方法计算了少数载流子浓度与Ge组分x、温度T以及掺杂浓度N的关系。发现常温时,在同一掺杂浓度下,少子浓度随Ge组分的增加而增大,其增加的速度越来越快;在同一Ge组分下,少子浓度随掺杂浓度的增加而减少,其减少的速度越来越慢。低温下,在考虑杂质不完全电离的同时,对由非简并情形向简并情形过渡的杂质电离出来的空穴浓度进行了修正,发现在同一Ge组分下,少子浓度随掺杂浓度的增加而增大,其增加的速度变得越来越快。同一掺杂浓度下,少子浓度随Ge组分的增加而增大,其增加的速度,轻掺杂时增加的较慢,重掺杂时增加得越来越快。     

Co掺杂SiC薄膜的紫外光敏特性

采用射频磁控溅射技术和复合靶材的方法,在p型单晶Si衬底上制备SiC薄膜及Co掺杂SiC薄膜。在真空度为1.0×10-4Pa、温度为1 200℃条件下,保温1 h进行晶化处理。通过X射线衍射(XRD)、X射线能量色散谱(EDX)、霍尔测量和紫外激光器等对薄膜的晶体结构、Co掺杂浓度、载流子浓度、导电类型及光敏特性等进行测试。结果表明,SiC薄膜为6H型晶体结构,Co掺杂后SiC薄膜的导电类型由n型转变为p型,载流子浓度比未掺杂的高2个数量级,对紫外光灵敏度是未掺杂的2倍,光照响应时间比未掺杂的缩短1/3。     

Stress, structural and electrical properties of Si-doped GaN film grown by MOCVD

The stresses, structural and electrical properties of n-type Si-doped GaN films grown by metalorganic chemical vapor deposition (MOCVD) are systemically studied. It is suggested that the main stress relaxation is induced by bending dislocations in low doping samples. But for higher doping samples, as the Si doping concentration increases, the in-plane stresses in the grown films are quickly relaxed due to the rapid increase of the edge dislocation densities. Hall effect measurements reveal that the carrier mobility first increases rapidly and then decreases with increasing Si doping concentration. This phenomenon is attributed to the interaction between various scattering process. It is suggested that the dominant scattering process is defect scattering for low doping samples and ionized impurity scattering for high doping samples.     

金属有机物化学气相淀积法生长的Si掺杂GaN薄膜的应力，结构与电学特性研究

The stresses, structural and electrical properties of n-type Si-doped GaN films grown by metaiorganic chemical vapor deposition （MOCVD） are systemically studied. It is suggested that the main stress relaxation is induced by bending dislocations in low doping samples. But for higher doping samples, as the Si doping concentration increases, the in-plane stresses in the grown films are quickly relaxed due to the rapid increase of the edge dislocation densities. Hall effect measurements reveal that the carrier mobility first increases rapidly and then decreases with increasing Si doping concentration. This phenomenon is attributed to the interaction between various scattering process. It is suggested that the dominant scattering process is defect scattering for low doping samples and ionized impurity scattering for high doping samples.