Substrate ramps and stepped stress transient measurements are applied to study vertical charge transport mechanisms in GaN-on-Si power HEMTs. By choosing appropriate bias points for substrate stress it is possible to single out the dominant charge transport mechanism: at low negative biases transport through carbon-doped GaN manifests itself in negative (decreasing) current transients with apparent activation energy (EA) = 0.29 eV, while at larger negative voltages transport through unintentionally doped GaN is characterized by positive (increasing) current transients (EA = 0.38 eV). We present experimental evidence for 3D variable range hopping taking place in C-doped GaN and 1D hopping along the dislocations in unintentionally doped GaN. By investigating transients obtained from bidirectional voltage steps of 10 V potential difference in the range 0 to -140 V, we observe that hopping transport through dislocations shows non-Ohmic behavior at low substrate biases, which manifests itself in a time constant τ strongly dependent on bias. We propose that this can be explained by the existence of a diode junction between the dislocation core and the 2D electron gas (2DEG).

中文翻译：

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硅基氮化镓高电子迁移率晶体管沟道层和缓冲层中的低场垂直电荷传输


衬底斜坡和阶梯应力瞬态测量用于研究 GaN-on-Si 功率 HEMT 中的垂直电荷传输机制。通过为衬底应力选择适当的偏置点，可以找出主要的电荷传输机制：在低负偏置下，通过碳掺杂 GaN 的传输表现为负（减少）电流瞬变，表观激活能 (EA) = 0.29 eV，而在较大的负电压下，通过无意掺杂的 GaN 传输的特点是正（增加）电流瞬变（EA = 0.38 eV）。我们提供了 C 掺杂 GaN 中发生 3D 可变范围跳变以及无意掺杂 GaN 中沿位错发生 1D 跳变的实验证据。通过研究从 0 至 -140 V 范围内 10 V 电位差的双向电压阶跃获得的瞬态，我们观察到通过位错的跳跃传输在低衬底偏压下表现出非欧姆行为，这表现为时间常数 τ 强烈依赖于偏见。我们认为这可以通过位错核心和二维电子气（2DEG）之间存在二极管结来解释。