Influence of growth conditions on the V-defects in InGaN/GaN MQWs

The influence of the growth temperature,TMIn/TEGa andⅤ/Ⅲratio on the V-defects of InGaN/GaN multi-quantum wells（MQWs） has been investigated and discussed.When the TMIn flow increases from 180 to 200 sccm,the density of V-defects increases from 2.72×10¹⁸ to 5.24×10¹⁸ cm^-2,and the V-defect width and depth increase too.The density also increases with the growth temperature.The densities are 2.05×10⁸,2.72×10¹⁸ and 4.23×10⁸ cm^-2,corresponding to a growth temperature of 748,753 and 758℃respectively.When the NH₃ flows are 5000,6600 and 8000 sccm,the densities of the V-defects of these samples are 6.34×10¹⁸,2.72×10¹⁸ and 4.13×10¹⁸ cm^-2,respectively.A properⅤ/Ⅲratio is needed to achieve step flow growth mode.We get the best quality of InGaN/GaN MQWs at a growth temperature of 753℃TMIn flow at 180 sccm,NH₃ flow at 6600 sccm,a flatter surface and less V-defects density.The depths of these V-defects are from 10 to 30 nm,and the widths are from 100 to 200 nm.In order to suppress the influence of V-defects on reverse current and electro-static discharge of LEDs,it is essential to grow thicker p-GaN to fill the V-defects.     

Effects of trimethylindium on the purity of In0.5Al0.5P and In0.5Al0.5as epilayers grown by metalorganic chemical vapor deposition

In_0.5Al_0.5P lattice-matched to GaAs and In_0.5A1_0.5As lattice-matched to InP epilayers were grown by atmospheric pressure metalorganic chemical vapor deposition (AP-MOCVD). The effect of trimethylindium on the purity of the as-grown layers was systematically studied using secondary ion mass spectroscopy (SIMS), deep level transient spectroscopy (DLTS), and capacitance-voltage (C-V) measurements. The SIMS results showed that oxygen is the main impurity in all layers and the oxygen concentration in InAlP was approximately one to four orders of magnitude higher than the oxygen concentration found in InALAs when the same indium source was used, indicating that more oxygen was introduced by the phosphine source than by the arsine source. Two electron traps in the InAlP epilayers and four electron traps in the InALAs epilayers were observed in this study. When a high-purity indium source was used, the best InAlP epilayer showed only one deep electron trap at 0.50 eV while the best InALAs epilayer showed no deep levels measured by DLTS. In addition, we also found that a high concentration of oxygen is related to the high resistivity in both material systems; this suggests that semi-insulating (SI) materials can be achieved by oxygen doping and high quality conducting materials can only be obtained through the reduction of oxygen. The oxygen concentration measured by SIMS in the best InALAs epilayer was as low as 3 × 10¹⁷ cm⁻³.     

Constant indium delivery from trimethylindium/hexadecane slurry

A previous publication describes trimethylindium (TMIn) delivery from a saturated solution in N,N-dimethyldodecylamine (dmda). The relatively constant delivery rate is attributed to evaporation of excess TMIn dissolved in the 1:1 TMIndmda complex. According to this explanation, TMIn must be appreciably soluble in a high-boiling solvent; e.g., TMIn is reported to dissolve to the extent of about 1.7 mole per mole of dmda at ambient temperature. Hexadecane, which dissolves only a negligible amount of TMIn (0.03 mol/mol at ambient temperature), was considered but not selected as a suitable solvent. Experimental tests of TMIn slurried in hexadecane demonstrate that relatively constant delivery rates can be obtained without high solubility. It is concluded that the liquid serves the purpose of a gas dispersing medium only, and any inert, high-boiling liquid should work.     

生长条件对InGaN/GaN多量子阱表面v型缺陷的影响

我们研究了生长温度、TMIn/TEGa和Ⅴ/Ⅲ比对 InGaN/GaN多量子阱表面v型缺陷的影响。当TMIn的流量从180sccm增加到200sccm,v型缺陷的密度也从2.7210¹⁸/cm² 增加到了5.2410¹⁸ /cm², v型缺陷的深度和宽度也随着TMIn流量的增加而增加。当生长温度从748℃增加到758℃, v型缺陷的密度分别是2.0510⁸/cm², 2.7210⁸/cm² 和 4.2310⁸/cm²,V型缺陷的密度随着生长温度的增加而增加。当NH3的流量从5000sccm增加到8000sccm, v型缺陷的密度分别为 6.3410¹⁸/cm², 2.7210¹⁸/cm², 4.1310¹⁸/cm²。我们在753℃, TMIn 流量为180sccm, NH3 流量为6600sccm时,得到了晶体质量最好的InGaN/GaN 多量子阱,表面平整,v型缺陷的密度也比较少。V型缺陷的深度从10nm到30nm,宽度从100nm到200nm,为了抑制v型缺陷对GaN基LEDs反向电流(IR)和静电放电 (ESD) 的影响,我们需要生长更厚的p-GaN来填充这些v型缺陷。     

Characterization of GaxIn1−xAs grown with TMIn

High quality Ga_xIn_1−xAs, lattice matched to InP, has been reproducibly grown by organometallic vapor phase epitaxy using trimethylgallium (TMGa), trimethylindium (TMIn), and AsH₃ in an atmospheric pressure reactor with no observable adduct formation. For the first time, using TMIn, room temperature electron mobilities of 10⁴ cm²/Vs and 77 K mobilities greater than 4 × 10⁴ cm²/Vs have beep obtained. Residual donor doping densities in the low 10¹⁵ cm⁻³ range have been routinely obtained. Material with excellent morphology has been grown from 540 to 670 C with the highest quality material being obtained near 650 C. The 4 K photoluminescence (PL) peak due to carbon is not seen in the material grown at higher temperatures; however, it increases dramatically as the growth temperature is lowered. This increased carbon incorporation leads to a sharp drop in the electron mobility, which exhibits a T^−0.5 behavior between 77 and 300 K. With optimum growth conditions, 4 K PL halfwidths of 4–5 meV are commonly observed. This high quality material is characterized by x-ray diffraction, PL, and Hall mobility measurements. Carbon and other impurity incorporation as a function of the growth parameters will be described.     

The impact of trimethylindium treatment time during growth interruption on the carrier dynamics of InGaN/GaN multiple quantum wells

Solid-state lighting through light emitting diodes (LEDs) is considered the next generation white-lighting. Because green light affects the quality of white light, significant improvement of the luminescence efficiency of green InGaN LEDs are crucial. In this study, the effects of trimethylindium (TMIn) treatment time during growth interruption on the emission and carrier dynamic characteristics of InGaN/GaN multiple quantum wells with green emission were investigated. TMIn treatment during growth interruption suppresses InGaN decomposition and indium aggregation such that more homogeneous indium composition, higher effective potential level, higher energy (localized) states, stronger photoluminescence (PL) intensity, and an apparent S-shaped variation of the temperature-dependent PL peak position were observed. In addition, as the treatment time increases, the decay time and its variation both become smaller. Because indium composition within the InGaN quantum wells is more homogeneous the longer the treatment time, weaker carrier transport and carrier-localized effects lead to a shorter decay time and better recombination efficiency. The research results provide important information to optimize the performance of green and white LEDs.     

Co-pyrolysjs of DIPSbH and TMIn

The reaction mechanisms for the pyrolysis of diisopropylantimonyhydride (DIPSbH, (C₃H₇)₂SbH) alone and for the co-pyrolysis of DIPSbH and trimethylindium (TMIn, (CH₃)₃In) in D₂ and H₂ ambients have been studied in an isothermal flow-tube, “ersatz” reactor using mass spectrometry to analyze the reaction products. The rate limiting step in the pyrolysis of DIPSbH alone is the reductive coupling reaction, producing C₃H₈. Additional products are C₃H₆ and C₆H₁₄produced by disproportionation and recombination reactions, respectively, of C₃H₇ radicals produced during the second stage of DIPSbH pyrolysis. The mixture of DIPSbH with TMIn produces a nonvolatile adduct on the quartz walls immediately after mixing in the reactor even at room temperature. No products were evolved at room temperature. However, for reactor temperatures between 100 and 200°C, an alkane elimination reaction occurs, producing CH₄. The remaining solid product is postulated to be [(CH₃)₂InSb(C₃H₇)₂]_n (n = 2 or 3). For temperatures greater than 200°C, the DIPSbH begins to pyrolyze independently. This temperature for the onset of DIPSbH pyrolysis is considerably above the temperature (125°C) at which pyrolysis begins for DIPSbH alone. This suggests that during co-pyrolysis formation of the adduct retards pyrolysis of DIPSbH. Apparently, dissociation of the adduct is necessary before the DIPSbH can pyrolyze independently. Co-pyrolysis of DIPSbH and TMIn between 250 and 375°C produces (C₃H₇)Sb(CH₃)₂ and (CH₃)₃Sb. Neither is found for the pyrolysis of DIPSbH alone. Considerably larger amounts of C₂H₆ are also detected at low temperatures (≤ 300°C). The ethane may come from the [(CH₃)₂InSb(C₃H₇)₂]_n via an intramolecular alkane elimination reaction. The high carbon contamination levels reported for InSb samples grown by OMVPE using these precursors at 300 and 325°C are postulated to be caused by the formation of (C₃H₇)Sb(CH₃)₂ during the co-pyrolysis of DIPSbH and TMIn, but not during the pyrolysis of each precursor alone.