A Restrain Method of Polarization Effect in GaN/AlGaN RTD

Abstract

Abstract-Polarization effects and polarization charges on the interfaces between GaN and AlGaN in GaN/AlGaN RTD on cplane GaN substrate destroy its RT conditions. To pave the way for electron transportation through GaN/AlGaN RTD in the mode of resonant tunneling, the influence from polarization effects was analyzed and a way to restrain it on the NDR characteristic was found. Since the polarization field is along the negative C crystal orientation, while the external applied field is orthogonal to the original crystal plane, the effective polarization field was modeled and device simulations of the polarization effects in GaN/AlGaN RTDs with different initial crystal planes of GaN substrates were carried out. The results indicate that to select an initial crystal plane of GaN substrate by increasing the c-plane drift angle from 0 to /2 is very helpful to recover and enhance the RT conditions since it is capable of reducing effective polarization field, forming RT quantum state energy levels on both sides of potential barriers and improving electron transmission. Therefore, the crystal planes between { 1 0 2 2 } and a-plane are optional as the initial crystal plane of GaN substrate for related power levels of related practical applications.

A novel quantum well RTD with intensive and continuous current oscillation in the bias voltage range higher than 3.15 V

“…As can be seen in Fig. 4, the simulated electric field distributions of the proposed device samples at different bias voltage are in accordance to Equation (5). The peak field at the emitter spacer-GaN barrier interface and the exponential electric field distribution in emitter spacer region are attributed to both the accumulation of electrons and existence of polarization field at bias voltages.…”

“…Fig.4, Equation(5) and Equation (6) also indicate that most part of bias voltage drops across the collector spacer region when it is thick enough. Moreover, the thickness of the collector spacer region Wcs has important impact on the current-voltage characteristic of the proposed RTD as illustrated in Fig.5by taking sample 2 for example.…”

“…signifies the charge increment in the i th layer at given bias voltage than in thermal equilibrium, i  signifies the pure polarization sheet charge density at i th interface and each can be calculated precisely and respectively as 1.4075e13 q/cm -2 , -5.4686e12 q/cm -2 , 1.3102e13 q/cm -2 and -7.4010e12 q/cm -2 by combining the nonlinear polarization model and Vegard's low according to the references [5,7,8].…”

“…As for the quantum devices for pure electron applications, dimensions of quantum well and barrier layers are much thinner than those of quantum devices for optical applications [1][2][3][4][5][6], which leads to much more significant quantum size effect since the dimensions of quantum well and barrier layers are much more closer to their de Broglie wavelengthes respectively on one hand and inner band carrier transportation mechanism dominants when sub-band energy level split occurs on the other hand.…”

A GaN/InGaN/AlGaN MQW RTD for versatile MVL applications with improved logic stability

“…Accompanying the development of III-nitrides materials and devices, increasing attention has been paid to the GaNbased resonate tunneling diode (RTD) because of its excellent properties such as wider direct band gap, larger band offset, higher peak electron velocity, higher critical breakdown voltage and higher thermal stability than those of GaAs/Al-GaAs and Si/GeSi counterparts [1][2][3][4][5][6][7][8][9][10] . In particular, conduction band offsets in the InGaN/AlGaN system are larger than those in the InGaAs/AlGaAs system and a built-in electric field exists owing to the piezoelectric polarization effects, the former appeared to have very interesting negative differential resistance (NDR) related properties and became considerably attractive during the last decade [1, 3-5, 7, 8, 10] .…”