Modeling Of Multi-channel GaN Heterostructure 2DEG And Energy Band Diagram

Ⅲ-nitride semiconductor materials are the main choice for the fabrication of new generation high electron mobility transistors because of their high carrier density,high mobility two-dimensional electron gas and high breakdown voltage.Meanwhile,multi-channel GaN heterostructures are widely used in high electron mobility transistors to achieve high transconductivity,low on-resistance and large output current.However,different heterostructures and polarities will lead to significant differences in device performance,and in some heterostructures,two-dimensional hole gas is also involved.Such a complicated situation make it difficult to model and analyze multi-channel high electron mobility transistor devices.In this work,an analytical model is developed to investigate the energy band diagram and the carrier population of multi-channel GaN heterostructure.With the help of the electric displacement vector continuity at each heterointerface,the Poisson equation and the electric neutrality of the entire heterostructure,the carrier density of each quantum well and the critical points of energy band diagram for any certain structure and polarity could be described.The common Ga-polar and N-polar multi-channel structures with intentional doping are calculated,and the cases where two-dimensional electron gas and two-dimensional hole gas exist simultaneously or separately in single channel are discussed.The calculation results of the model in this work will be compared with the widely used Schr（?）dinger-Poisson self-consistent solution or the Atlas@Silvaco commercial software to verify the feasibility of the model.The specific work results of this paper are as follows:1.Modeling the energy band diagram and two-dimensional electron gas population of Ga-polar multi-channel GaN heterostructures.Single-channel and multi-channel common high electron mobility transistor structures with only two-dimensional electron gas in each channel are calculated.The modeling methods of Al GaN back barrier,GaN cap layer,Al N insertion layer,and In GaN insertion layer exist simultaneously or separately in the heterostructures are discussed,two-dimensional hole gas and its quantum wells are modeled using a method similar to two-dimensional electron gas.In addition,an unintentionally doped P-channel high electron mobility transistor structure using an In GaN channel was modeled.2.Through the established Ga-polar model,the influence of the two-dimensional electron gas population of single-channel and double-channel heterostructures on the substrate stress was studied,and the change of two-dimensional electron gas concentration caused by the shift of spectral beam of₂peak from Raman spectra is theoretically calculated.It is calculated that when the₂peak position changes by 2cm^-1,the lattice constant“(6”of the GaN buffer layer is strained by about 0.1%,and the spontaneous polarization changes of Al N barrier layer and GaN channel are in opposite directions.The sum of polarized charges at the Al N/GaN interface changed by about 1.6%,but the total 2DEG density changed by only about 0.9%.3.Model the energy band diagram and carrier population of N-polar multi-channel GaN heterostructures.The energy band diagram and carrier distribution of N-polar GaN from single-channel to multi-channel heterostructures are calculated and the two-dimensional carrier gas of electrons and holes is considered simultaneously,and the existence condition of two-dimensional hole gas is discussed numerically.The coexistence of two carrier gases or only one carrier gas in the single channel is calculated respectively,and the intentional doping of the buffer layer and the barrier layer is also included in the model.In summary,in this work an analytical model of multi-channel heterojunctions covering Ga-polar and N-polar is proposed,which contains the case where two kinds of carriers exist in one single channel separately and simultaneously,and the common insertion Layer structure and doping are taken into account.The model establishes the numerical relationship between electric field,energy bands and carriers through the continuity of the electric displacement vector at the heterojunction interface and the electric neutrality balance of the whole heterostructure.Compared with the commonly used Schrodinger-Poisson equation self-consistent solution and Atlas simulation software,the model proposed in this paper will be completely composed of material physical parameters and is more intuitive,which is helpful to understand the principle of GaN high electron mobility transistor devices and guide device design.