講演情報
[15a-K101-6]Study of interface trap density in Ge quantum devices
〇(D)Chutian Wen1, Yuto Arakawa1, Ryutaro Matsuoka1, Raisei Mizokuchi1, Jun Yoneda2, Tetsuo Kodera1 (1.Institute of Science Tokyo, 2.University of Tokyo)
キーワード：
Ge quantum well、Dielectric film、Interfcae trap
Ge Hole spin qubit has shown potential for realizing high speed qubit operation and large-scale qubit integration. However, the strong spin-orbit coupling, which couples the spin degree of freedom to the electrical noise, poses challenges in maintaining high qubit fidelity while achieving the high-speed operation. Interface traps, a major source of electrical noise in the Ge quantum dots, therefore need to be studied to gain a comprehensive understanding of how to achieve long-term stable qubit operations.
In the previous report, people pointed out that higher atomic layer deposition (ALD) temperature results in a lower interface trap density. Additionally, the application of oxygen plasma pretreatment and pre-cleaning trimethyl-aluminum (TMA) pulse are considered beneficial for oxidizing the Si cap and removing the GeOx, respectively. These treatments are potentially effective in reducing the interface trap density and, hence, improving the stability of the Ge quantum devices. Therefore, in this work, we applied these techniques and fabricated Hall bar devices with gate oxide film of Al2O3 deposited under different conditions on a Ge/SiGe heterostructure. We conduct a systematic discussion on the effect of ALD temperature (250℃ and 150℃), oxygen plasma pretreatment, and TMA pre-cleaning on the quality of Al2O3 to identify the condition that enables the lowest interface trap density through capacitance-voltage measurements. Furthermore, we investigate the dependence of hole mobility on carrier density, along with the percolation density, to demonstrate that a lower interface trap density gets the influence of surface tunneling effect suppressed. This study makes contributions to realizing a stable qubit environment in a Ge-based quantum dot system.
In the previous report, people pointed out that higher atomic layer deposition (ALD) temperature results in a lower interface trap density. Additionally, the application of oxygen plasma pretreatment and pre-cleaning trimethyl-aluminum (TMA) pulse are considered beneficial for oxidizing the Si cap and removing the GeOx, respectively. These treatments are potentially effective in reducing the interface trap density and, hence, improving the stability of the Ge quantum devices. Therefore, in this work, we applied these techniques and fabricated Hall bar devices with gate oxide film of Al2O3 deposited under different conditions on a Ge/SiGe heterostructure. We conduct a systematic discussion on the effect of ALD temperature (250℃ and 150℃), oxygen plasma pretreatment, and TMA pre-cleaning on the quality of Al2O3 to identify the condition that enables the lowest interface trap density through capacitance-voltage measurements. Furthermore, we investigate the dependence of hole mobility on carrier density, along with the percolation density, to demonstrate that a lower interface trap density gets the influence of surface tunneling effect suppressed. This study makes contributions to realizing a stable qubit environment in a Ge-based quantum dot system.