Effect of threading dislocation density on Ni/n-GaN Schottky diode I-V characteristics
Effect of threading dislocation density on Ni/n-GaN Schottky diode I-V characteristics
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DOI：
10.1063/1.2219985
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发表时间：
2006-07-15
影响因子：
3.2
通讯作者：
Ringel, S. A.
中科院分区：
文献类型：
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作者：
Arehart, A. R.;Moran, B.;Ringel, S. A.
采用正向偏置电流-电压-温度（I-V-T）和内部光电发射（IPE）测量方法研究了穿透位错密度对Ni/n-GaN肖特基势垒二极管特性的影响。名义上，在蓝宝石衬底上的两种类型的GaN模板上生长相同的金属有机化学气相沉积生长的GaN层，以可控地将穿透位错密度（TDD）从3 × 10（7）cm（-2）变化到7 × 10（8）cm（-2）。I-V-T测量结果表明，电子发射是主要的传输机制，理想因子在室温下接近1.01的两种样品类型。肖特基势垒高度显示出与TDD类似的不变性，从拟合I-V-T结果到电子发射扩散模型获得的测量值为1.12-1.13 eV。I-V-T结果通过在相同二极管上进行的IPE测量进行了验证，证实了Ni/n-GaN势垒高度对于此处测量的TDD范围没有显示出可测量的TDD依赖性。与该结果明显相反的是，所测量的正向偏置I-V特性指示所观察到的正向偏置导通电压的偏移，使得在这里研究的较高TDD值处，观察到较大的导通电压（较低的电流）。这种差异是由于局部电流阻塞周围的贯穿位错的Ni/GaN界面相交的高势垒区域。提出了一个简单的模型，调和所观察到的电压漂移和变化提取的理查森常数作为一个函数的线程位错密度。利用该模型，获得了类似于0.2 V的平均局部势垒周围的位错，这将分流电流流过正向偏置肖特基界面的nondislocated区域。(c)2006年，美国物理学会。
The impact of threading dislocation density on Ni/n-GaN Schottky barrier diode characteristics is investigated using forward biased current-voltage-temperature (I-V-T) and internal photoemission (IPE) measurements. Nominally, identical metal-organic chemical vapor deposition grown GaN layers were grown on two types of GaN templates on sapphire substrates to controllably vary threading dislocation density (TDD) from 3x10(7) to 7x10(8) cm(-2). I-V-T measurements revealed thermionic emission to be the dominant transport mechanism with ideality factors near 1.01 at room temperature for both sample types. The Schottky barrier heights showed a similar invariance with TDD, with measured values of 1.12-1.13 eV obtained from fitting the I-V-T results to a thermionic emission-diffusion model. The I-V-T results were verified by IPE measurements made on the same diodes, confirming that the Ni/n-GaN barrier heights do not show a measurable TDD dependence for the TDD range measured here. In apparent contrast to this result is that the measured forward bias I-V characteristics indicate a shift in the observed forward bias turn-on voltage such that at the higher TDD value investigated here, a larger turn-on voltage (lower current) is observed. This difference is attributed to localized current blocking by high potential barrier regions surrounding threading dislocations that intersect the Ni/GaN interface. A simple model is presented that reconciles both the observed voltage shift and variations in the extracted Richardson constant as a function of threading dislocation density. With this model, an average local barrier surrounding dislocation of similar to 0.2 V is obtained, which diverts current flow across the forward biased Schottky interface to nondislocated regions. (c) 2006 American Institute of Physics.