Study on the Physical and Leakage Current Characteristics of an Optimized High-k/InAlAs MOS Capacitor with a HfO2–Al2O3 Laminated Dielectric

Abstract

High-k/n-InAlAs MOS capacitors are popular for the isolated gate of InAs/AlSb and InAlAs/InGaAs high-electron mobility transistors. In this study, a new kind of high-k/n-InAlAs MOS-capacitor with a HfO2–Al2O3 laminated dielectric was successfully fabricated using an optimized process. Compared with the traditional HfO2/n-InAlAs MOS capacitor, the new device has a larger equivalent oxide thickness. Two devices, with a HfO2 (8 nm)–Al2O3 (4 nm) laminated dielectric and a HfO2 (4 nm)–Al2O3 (8 nm) laminated dielectric, respectively, were studied in comparison to analyze the effect of the thickness ratios of HfO2 and Al2O3 on the performance of the devices. It was found that the device with a HfO2 (4 nm)–Al2O3 (8 nm) laminated dielectric showed a lower effective density of oxide charges, and an evidently higher conduction band offset, making its leakage current achieve a significantly low value below 10−7 A/cm2 under a bias voltage from −3 to 2 V. It was demonstrated that the HfO2–Al2O3 laminated dielectric with a HfO2 thickness of 4 nm and an Al2O3 thickness of 8 nm improves the performance of the high-k dielectric on InAlAs, which is advantageous for further applications.

Leakage Current Conduction Mechanism of Au-Pt-Ti/ HfO2-Al2O3/n-InAlAs Metal-Oxide-Semiconductor Capacitor under Reverse-Biased Condition

“…The device structure from bottom to top is a 350 µm semi-insulating InP substrate, a 200 nm InP buffer layer, a 500 nm Si-doped In 0.5 Al 0.5 As semiconductor layer with a doping concentration of 1 × 10 17 cm −3 [15], a 12 nm oxide layer with Al 2 O 3 -HfO 2 dielectrics, and a metal with structure of Ti (20 nm)/Pt (20 nm)/Au (200 nm). The detailed schematic layer structures of the prepared sample can be found in our previous published paper [14]. In order to identify the impact of the thickness of the Al 2 O 3 inserting layer, we manufactured two kinds of samples with an oxide layer of HfO 2 (4 nm)/Al 2 O 3 (8 nm) laminated dielectrics (marked as Sample #1), and HfO 2 (8 nm)/Al 2 O 3 (4 nm) laminated dielectrics (marked as Sample #2), respectively.…”

“…HfO 2 that presents a high dielectric constant is a popular candidate as the high-k dielectric [8][9][10], however it does not match well with InAlAs and the poor lattice match would degrade its performance [9]; Al 2 O 3 is used frequently as the high-k dielectric as well [10,11], however its dielectric constant is not high enough, and that will lead to a lower EOT (effective oxide thickness) which is not beneficial for reducing device size. For improvement, the HfO 2 -Al 2 O 3 laminated dielectric layer is proposed, and in this new device structure, a compromised dielectric constant can be achieved and the leakage current can be effectively suppressed [12][13][14]. In our previous paper [13], the physical and electrical performance of the new Au-Pt-Ti/high-k/n-InAlAs MOS capacitors with HfO 2 -Al 2 O 3 laminated dielectric were studied in detail.…”

Channel Characteristics of InAs/AlSb Heterojunction Epitaxy: Comparative Study on Epitaxies with Different Thickness of InAs Channel and AlSb Upper Barrier

“…As another typical antimony material, AlSb has little lattice mismatch with InAs, but its band gap of 1.27 eV with InAs can form very deep electron potential wells, and makes the InAs/AlSb heterogeneous structures possess a high concentration of two-dimensional electron gas density (2DEG). Therefore, InAs/AlSb high electron mobility transistors (HEMTs) devices, with AlSb as a barrier layer and InAs as the channel layer, have excellent physical properties, such as ultra-high cutoff frequency, very low power consumption and good noise performance, and present a very good application prospect in analog/digital circuit, microwave field and space communication [1][2][3][4][5]. As we know, the properties of HEMTs are fundamentally determined by the performance of epitaxial materials.…”

Nanoscale dielectric properties of TiO2 in SiO2 nanocomposite deposited by hybrid PECVD method

“…In a second approach, high-k multilayers stacking or nanolaminates were investigated since they lead to a reduction in leakage current and an increase in ε r which depends on the number of layers [1]. Studies on various dielectric stacks are reported in the literature, mainly developed by Atomic Layer Deposition (ALD), as TiO 2 -Al 2 O 3 [9], HfO 2 -Al 2 O 3 [10], VO 2 -SiO 2 [11], Ta 2 O 5 -HfO 2 [12], ZrO 2 -HfO 2 [12], Ta 2 O 5 -ZrO 2 [12], HfO 2 -SiO 2 [13] or ZrO 2 -La 2 O 3 [14]. These stacks associate layers of high-k materials with highly insulating ones as SiO 2 or Al 2 O 3 [15].…”