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Study on the polarity control of hexagonal-structure widegap compound semiconductors and its effect on the material control

六方结构宽禁带化合物半导体极性控制及其对材料控制的影响研究

基本信息

批准号：
13450121
负责人：
YOSHIKAWA Akihiko
金额：
$ 9.6万
依托单位：
Chiba University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2004
项目状态：
已结题

项目摘要

Widegap compound semiconductors such as GaN have the hexagonal wurtzite structure and are lack in symmetry along the c-axis. Reflecting this property, the epitaxy process itself and many properties of these materials were greatly affected by the polarity/direction during growth. However, the mechanism for the polarity selection and its control during growth of these materials were not clear.In this research, first we investigated the polarity control mechanism in both MOVPE and MBE of GaN, and we proposed a successful method for the polarity inversion from N-polarity to Ga-polarity, where Al-bilayer played an important role. It was found that the All-covered surface was chemically/thermally stable and Al-bilayer could be frozen into the crystal during growth.Next, the polarity control of ZnO was investigated. The polarity control of oxides was complicated compared to that of nitrides. This was partly attributed to the fact that oxides tended to be amorphous, in particular at low temperatures, the ZnO buffer deposited at low-temperatures sometimes could not keep the epitaxy relationship between the substrate and epilayer. We proposed to use nitrides as buffer layers resulting in successful polarity control.Finally we extended our work to the InN epitaxy for the first time and we clarified that the N-polarity growth regime was preferable in the epitaxy of InN itself and its material control as well. This was because the InN easily decomposes at such low temperatures below 500 C but the epitaxy temperature for the N-polarity growth could be as high as 600 C, which was about 100 deg higher than that of In-polarity growth. On the basis of these results, we succeeded in growth of device-quality InN, InN-based ternary alloys, such as InGaN and InAlN, and very fine structure SQW/MQW consisted of InN/InGaN and InN/InAlN heterostructures for the first time.

氮化镓等宽隙化合物半导体具有六方纤锌矿结构，沿c轴缺乏对称性。在生长过程中，极性/方向对外延过程本身和材料的许多性能有很大的影响，这反映了这种特性。然而，这些材料在生长过程中的极性选择及其控制机制尚不清楚。在本研究中，我们首先研究了GaN在MOVPE和MBE中的极性控制机制，并提出了一种成功的从n极性到ga极性的极性反转方法，其中al双分子层发挥了重要作用。结果表明，全覆盖表面是化学/热稳定的，在生长过程中，双分子层可以被冻结成晶体。其次，研究了ZnO的极性控制。氧化物的极性控制较氮化物复杂。这在一定程度上是由于氧化物倾向于非晶化，特别是在低温下，低温下沉积的ZnO缓冲液有时不能保持衬底和外延层之间的外延关系。我们建议使用氮化物作为缓冲层，从而成功地控制极性。最后，我们首次将我们的工作扩展到InN外延，并澄清了n极性生长机制在InN本身的外延及其材料控制中也是可取的。这是因为InN在低于500℃的低温下容易分解，而n极性生长的外延温度可高达600℃，比内极性生长的外延温度高约100℃。在这些结果的基础上，我们成功地生长出了器件级的InN、InN基三元合金，如InGaN和InAlN，以及首次由InN/InGaN和InN/InAlN异质结构组成的非常精细的SQW/MQW。