AlGaN/GaN HFET的优化设计

从自洽求解薛定谔方程和泊松方程出发研究了不同掺杂方式下异质结能带和二维电子气的行为。发现掺杂能剪裁异质结能带的弯曲度、控制电子气的二维特性和浓度。在此基础上研究了不同掺杂方式的掺杂效率。通过掺杂和势垒结构的优化设计,得出了用δ掺杂加薄AlN隔离层的结构,既提高了电子气浓度,又保持电子气的强二维特性。从电子气浓度和栅对电子气的控制力度出发,提出了HFET势垒优化设计中的电子气浓度与势垒层厚度乘积规则。依据二维表面态理论,研究了表面态随帽层掺杂结构的变化。从前述乘积规则和表面态变化出发进行了内、外沟道异质结构的优化设计。优化结构既提高了电子气浓度和跨导,降低了欧姆接触电阻,又抑制了电流崩塌。

Optimized Design of AlGaN/GaN HFET

From self-consistent solution of Schro dinger equation and Poisson equation the band structure and the behavior of two-dimensional electron gases for AlGaN/GaN heterostructures with different doping structure are investigated.It is found that the band structure winding and two-dimensional electron gases are controlled by the doping structures,from which the doping efficiency for different doping models is compared.By using the optimized design of doping and heterostructures,a heterostructure with δ doping and thin AlN exclusion layer is proposed,which not only increases the electron density but also strengthens the two-dimensional degree of electron.Considering the controllability of two-dimensional electrons during the RF operation of HFET,a product of electron density and barrier width is proposed as a criterion for heterostructure design.Based on the two-dimensional surface state theory the surface states under different doping concentration in surfacing layer are calculated.According to the criterion of heterostructures design and two-dimensional surface state behaviors an optimized heterostructure design for current-collapse-free HFET is given.