An analysis of the 2DEG (Dimensional Electron Gas)-emitter heterojunction bipolar transistor

The AlGaAs/GaAs 2DEG (Dimensional Electron Gas)-emitter HBT is thoroughly examined from the device characterization, modeling and operation perspectives. This unique device structure gives formation of 2DEG in emitter-base heterojunction interface of the device compared to conventional HBTs. And the 2DEG plays a pivotal role in overall device operation and modeling process. For example, drastically reduced low offset voltage with high current gain can be obtained without adopting complicated processing method. The accurate calculation of 2DEG density is crucial factor to understand the device operation. The Non-Linear Average Field (NLAF) quasi-triangular quantum well approximation model--simply "NLAF model"--is proposed for this purpose. The model was calculated on the basis of AlGaAs/GaAs system but diverse materials systems could be utilized by substitution of material and device parameters of the device. The validation of modeling scheme is examined under different device operating conditions. The assumptions are made according to device working conditions which are prone to fabrication processes and device structural modifications. The significance of this modeling is qualitatively explained on the basis of simulation results. All the simulation results are compared between various modeling schemes with different device operating conditions. These comprehensive examinations give thorough understanding of device operation and modeling processes.