Defect assistant band alignment transition from staggered to broken gap in mixed As/Sb tunnel field effect transistor heterostructure

Abstract

Articles you may be interested inTunneling field-effect transistor with Ge/In0.53Ga0.47As heterostructure as tunneling junction J. Appl. Phys. 113, 094502 (2013) The compositional dependence of effective tunneling barrier height (E beff ) and defect assisted band alignment transition from staggered gap to broken gap in GaAsSb/InGaAs n-channel tunnel field effect transistor (TFET) structures were demonstrated by x-ray photoelectron spectroscopy (XPS). High-resolution x-ray diffraction measurements revealed that the active layers are internally lattice matched. The evolution of defect properties was evaluated using cross-sectional transmission electron microscopy. The defect density at the source/channel heterointerface was controlled by changing the interface properties during growth. By increasing indium (In) and antimony (Sb) alloy compositions from 65% to 70% in In x Ga 1Àx As and 60% to 65% in GaAs 1Ày Sb y layers, the E beff was reduced from 0.30 eV to 0.21 eV, respectively, with the low defect density at the source/channel heterointerface. The transfer characteristics of the fabricated TFET device with an E beff of 0.21 eV show 2Â improvement in ON-state current compared to the device with E beff of 0.30 eV. On contrary, the value of E beff was decreased from 0.21 eV to À0.03 eV due to the presence of high defect density at the GaAs 0.35 Sb 0.65 /In 0.7 Ga 0.3 As heterointerface. As a result, the band alignment was converted from staggered gap to broken gap, which leads to 4 orders of magnitude increase in OFF-state leakage current. Therefore, a high quality source/channel interface with a properly selected E beff and well maintained low defect density is necessary to obtain both high ON-state current and low OFF-state leakage in a mixed As/Sb TFET structure for high-performance and lower-power logic applications. V C 2012 American Institute of Physics. [http://dx

Investigation of analog/RF performance of staggered heterojunctions based nanowire tunneling field-effect transistors

“…The theoretical insights of staggered heterojunction (HETJ) based TFETs to achieve S < 60mv/dec at room temperature with an improved I ON has been already reported [26][27][28]. Among various III-V based staggered heterostructures, the bandgap and band alignment of the mixed As/Sb based heterostructures can be tailored-made over a wide range by carefully controlling the alloy compositions in the mixed As/Sb material system [29]. Thus, mixed As/Sb Inx Ga1-x As/GaAsySb1-y staggered gap heterostructure appears to be one of the most promising material system to boost the TFET performance due to its superior device performance.…”

“…As a result, OFF-state current I OFF will increase and I ON /I OFF will decrease. Moreover, due to increased interface trap densities, trap assisted tunneling (TAT) current will increase, causing an enhancement in the OFF-state leakage current [29], thus causing a reduction in the I ON /I OFF ratio and subthreshold swing degradation.…”

Design, fabrication, and analysis of p-channel arsenide/antimonide hetero-junction tunnel transistors

“…A proper switching sequence of III/V elements is critical for engineering an abrupt hetero-interface during the growth of mixed As/Sb materials, [25][26][27] otherwise the intermixing between As and Sb atoms will result in uncontrolled layer composition at the hetero-interface, which will cause the change of strain relaxation properties of the epilayer grown on this interface. 28 The change of strain relaxation properties may introduce high density dislocations at the hetero-interface and within the InAs source layer, which explains the high I OFF in the fabricated hetJ pTFET. Besides, the formation of GaAs 0.022 Sb 0.978 layer at the hetero-interface will change the band alignment of source/channel, which leads to the increase of tunneling distance and degrade the device performance.…”

Extracting the effective bandgap of heterojunctions using Esaki diode I-V measurements

“…2 E g,eff is usually determined from the electron affinities and bandgaps of the bulk materials, 3 or using optical measurements. 4,5 However, there is significant uncertainty on E g,eff , especially for the heterostructure In 0.53 Ga 0.47 As/ GaAs 0.5 Sb 0.5 (InGaAs/GaAsSb, Fig. 1), which makes the prediction of TFET performance difficult.…”

“…5 for a In 0.7 Ga 0.3 As/ GaAs 0.35 Sb 0.65 heterojunction. It was reported that a fixed positive charge of 6 Â 10 12 cm À2 changed the band alignment from staggered to broken.…”