Measurement of the hot electron mean free path and the momentum relaxation rate in GaN
Measurement of the hot electron mean free path and the momentum relaxation rate in GaN
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DOI：
10.1063/1.4905367
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发表时间：
2014-12
影响因子：
4
通讯作者：
D. J. Suntrup;G. Gupta;Haoran Li;S. Keller;U. Mishra
中科院分区：
文献类型：
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作者：
D. J. Suntrup;G. Gupta;Haoran Li;S. Keller;U. Mishra
我们提出了一种使用热电子晶体管 (HET) 测量平均自由程并提取 GaN 中热电子动量弛豫时间的方法。在该器件中，电子通过高能发射极势垒注入基极，在基极上电子经历远高于导带边缘的准弹道输运。穿过基极后，高能电子要么超越基极-集电极势垒并成为集电极电流，要么从势垒反射并成为基极电流。我们制造具有不同基极厚度的 HET，并测量每个器件的共发射极传输比 (α)。通过将 α 拟合为基础宽度函数的衰减指数来提取平均自由程，并使用合适的注射速度计算弛豫时间。对于注入能量为 ∼1 eV 的器件，我们测量了 14 nm 的热电子平均自由程，并计算出 16 fs 的动量弛豫时间。这些值与理论计算一致，其中纵向光学声子散射是主要的动量弛豫机制。
We present a method for measuring the mean free path and extracting the momentum relaxation time of hot electrons in GaN using the hot electron transistor (HET). In this device, electrons are injected over a high energy emitter barrier into the base where they experience quasi-ballistic transport well above the conduction band edge. After traversing the base, high energy electrons either surmount the base-collector barrier and become collector current or reflect off the barrier and become base current. We fabricate HETs with various base thicknesses and measure the common emitter transfer ratio (α) for each device. The mean free path is extracted by fitting α to a decaying exponential as a function of base width and the relaxation time is computed using a suitable injection velocity. For devices with an injection energy of ∼1 eV, we measure a hot electron mean free path of 14 nm and calculate a momentum relaxation time of 16 fs. These values are in agreement with theoretical calculations where longitudinal optical phonon scattering is the dominant momentum relaxation mechanism.