Quantum capacitance effect is observed in nanostructured material stacks with quantum limited density of states. In contrast to conventional structures where two-dimensional electron gases (2DEG) with reduced density of states interact with a metal plate, here we explore the quantum capacitance effect in a unique structure formed by two 2DEG in a graphene sheet and AlGaN/GaN quantum well. The total capacitance of the structure depends non-linearly on the applied potential and the linear density of states in graphene leads to enhanced electric field leakage into the substrate causing a dramatic 50% drop in the overall capacitance at low bias potentials. We show theoretical projections of the quantum capacitance effect in the proposed device stack, fabricate the structure and provide experimental verification of the calculated values at various temperatures and applied potentials. The wide swing in the total capacitance is sensitive to the chemical potential of the graphene sheet and has multiple applications in molecular sensing, electro-optics, and fundamental investigations.

在具有量子限制态密度的纳米结构材料堆叠中观察到量子电容效应。与具有降低的态密度的二维电子气 (2DEG) 与金属板相互作用的传统结构相比，这里我们探索了由石墨烯片中的两个 2DEG 和 AlGaN/GaN 量子阱形成的独特结构中的量子电容效应. 该结构的总电容非线性取决于施加的电位，石墨烯中的线性状态密度导致增强的电场泄漏到基板中，导致在低偏置电位下总电容急剧下降 50%。我们展示了所提出的器件堆栈中量子电容效应的理论预测，制造结构并提供在不同温度和施加电位下的计算值的实验验证。总电容的大幅波动对石墨烯片的化学势敏感，在分子传感、电光和基础研究中具有多种应用。