Abstract
This paper discusses the influence of Sb/In ratio on the transport properties and crystal quality of the 200 nm InAsxSb1-x thin film. The Sb content of InAsxSb1-x thin film in all samples was verified by HRXRD of the symmetrical 004 reflections and asymmetrical 115 reflections. The calculation results show that the Sb component was 0.6 in the InAsxSb1-x thin film grown under the conditions of Sb/In ratio of 6 and As/In ratio of 3, which has the highest electron mobility (28 560 c
High-speed devices using III-V compound materials have become one of the international research hotspot
Since the InAsSb material contains two V elements of As and Sb, the composition of group V elements cannot be accurately calculated by the ratio of growth rates. More influencing factors need to be considered when growing InAsSb materials because the adhesion of As and Sb elements varies under different growth conditions. Therefore, it is necessary to study the composition control of InAsSb materials grown by molecular beam epitaxy. Based on the theoretical calculation results reported in the current literatur
This paper discusses the influence of Sb/In ratio on the transport properties and crystal quality of the 200 nm InAsxSb1-x thin film. The Sb content of InAsxSb1-x thin film in all samples was verified by HRXRD via the symmetrical 004 reflections and asymmetrical 115 reflections. In addition, the influence of Sb/In ratio and As/In ratio on the transport properties and crystal quality of Al0.2In0.8Sb/ InAsxSb1-x quantum well heterostructures has also been investigated. By optimizing the Sb/In ratio and As/In ratio, Al0.2In0.8Sb/ InAsxSb1-x quantum well heterostructures with good surface morphology and high electron mobility were obtained. All samples were confirmed by atomic force microscopy (AFM), high-resolution X-ray diffraction (HRXRD), reciprocal space map (RSM) and Hall measurement.
All samples were grown on GaAs substrate by Gen-II solid-source MBE system. After deoxidation of GaAs substrate at 690 ℃ for 5 minutes, a 100 nm GaAs was grown at 650 ℃ and a 100 nm GaSb was grown at 540 ℃ to ensure that the substrate surface was flat. For one structure, a 1.5 μm Al0.2In0.8Sb metamorphic buffer layer was used to study the transport properties of the 200 nm InAsxSb1-x layer, as shown in

Fig.1 Schematic diagram of InAsxSb1-x thin film structure
图1 InAsxSb1-x薄膜结构示意图
For another structure, the Al0.2In0.8Sb/ InAsxSb1-x quantum well heterostructures were grown for preparing high electron mobility transistors, as shown in

Fig.2 Schematic diagram of Al0.2In0.8Sb/ InAsxSb1-x quantum well heterostructures
图2 Al0.2In0.8Sb/ InAsxSb1-x量子阱异质结构示意图
The first group of samples B1, B2, and B3 with different Sb/In ratios (5,6,7) were grown to investigate the effects of different Sb components on the crystal quality and electron mobility of Al0.2In0.8Sb/ InAsxSb1-x quantum well heterostructures, while the As/In ratio was also kept at about 3. Meanwhile, the channel thickness of this group of samples was 15 nm.The second group of samples C1, C2, and C3 with different As/In ratios (1,2,3) were grown to investigate the effects of different As components on the crystal quality and electron mobility of Al0.2In0.8Sb/InAsxSb1-x quantum well heterostructures, while the Sb/In ratio was kept at about 6. Meanwhile, the channel thickness of this group of samples was increased from 15 nm to 30 nm. The third group of samples D1, D2, D3, D4 and D5 corresponds to InAs0.4Sb0.6 channel layer thicknesses of 15, 20, 25, 30 and 35 nm to investigate the effect of different channel thicknesses on the crystal quality and electron mobility of Al0.2In0.8Sb/ InAsxSb1-x quantum well heterostructures. The Sb/In ratio was kept at about 6 and the As/In ratio was kept at about 3.

(a)

(b)
Fig.3 (a) 2×2 μ
图3 (a)样品A1、A2、A3的2×2 μm2 AFM扫描图像;(b)样品A1、A2、A3的10×10 μm2 AFM扫描图像
The Sb content of the InAsxSb1-x layer in all samples was verified by HRXRD via the symmetrical 004 reflections and asymmetrical 115 reflections, as shown in Fig.
Sample | (004)scanning | (115)scanning | a(Å) | 1-X | ||
---|---|---|---|---|---|---|
Bragg angle | a⊥(Å) | Bragg angle | a//(Å) | |||
A1 | 29.06° | 6.3435 | 39.08° | 6.3491 | 6.3464 | 0.68 |
A2 | 29.08° | 6.3395 | 39.62° | 6.2765 | 6.3068 | 0.6 |
A3 | 28.73° | 6.41 | 38.64° | 6.4099 | 6.4099 | 0.84 |
The crystalline quality of the epitaxial layers was further assessed by XRD RSM measurements.

(a)

(b)
Fig. 4 HRXRD scanning curves of (a) (004) peak and (b) (115) peak for various samples.
图4 样品的HRXRD:(a)(004)扫描和(b)(115)扫描

Fig.5 XRD RSMs of the symmetrical (004) (a) sample A1; (b) sample A2 and (c) sample A3
图5 对称扫描(004)(a)样品A1;(b)样品A2和(c)样品A3的XRD-RSM
The influence of the V/III ratio on the electrical properties of InAsxSb1-x thin films was examined by determining the Hall properties. The electron mobility μ refers to the average speed of electron units under the electric field intensity. The value of μ can be obtained from the following formula:
, | (1) |
where m* represents the electron effective massive, τ represents the mean free time of electrons and q represents electron charge. InAsxSb1-x is a compound of InSb and InAs materials, so its crystal structure is relatively stable. The room temperature electron effective mass of InAsxSb1-x is 0.023-0.039(1-x)+0.03(1-x

Fig.6 Electron mobility μ and 2DEG concentrations ns versus different Sb/In ratios for samples A1, A2, A3
图6 样品A1,A2和A3的电子迁移率和二维电子气浓度与不同的Sb/In比
Ref | Sb composition | Thickness (nm) | RMS roughness (nm) | Electron mobility (c | 2DEG concentrations (c |
---|---|---|---|---|---|
| 0.58 | 1 500 |
1.9(10×10 μ | - | - |
| 0.13 | 5 000 | - | 25 000 |
5 × 1 |
| 0.05 | 800 |
3.954(2×2 μ | 5 430 |
1.01×1 |
| 0.9 | 1 000 |
1.99(10×10 μ | 13 000 |
1.3×1 |
This work | 0.6 | 200 |
0.7(10×10 μ | 28 560 |
1.01 ×1 |
Although InAsSb has excellent transmission properties, the lack of matching high-quality semi-insulating substrates limits its development. Therefore, an Al0.2In0.8Sb strain buffer layer was used to release the stress caused by the lattice mismatch between InAsSb and GaAs substrates. The AFM images of Al0.2In0.8Sb/InAsxSb1-x quantum well heterostructures grown under different Sb/In ratios are shown in

Fig.7 10×10 μ
图7 样品B1, B2, B3的10×10 μm2 AFM扫描图像
The (004) HRXRD scanning curves of samples with different Sb components are shown in

Fig.8 HRXRD scanning curves of (004) peak for samples B1, B2, B3
图8 样品B1、B2、B3的(004)峰HRXRD扫描曲线
As shown in

Fig.9 Electron mobility μ and 2DEG concentrations ns versus different Sb/In ratios
图9 电子迁移率μ和2DEG浓度ns与不同Sb/In比的关系
It can be observed from the comparison between

Fig.10 10×10 μ
图10 样品C1、C2、C3的10×10 μm2 AFM图像
The (004) HRXRD scanning curves of samples with different As components are shown in

Fig.11 HRXRD scanning curves of (004) peak for samples C1, C2, C3
图11 样品C1、C2、C3的(004)峰HRXRD扫描曲线
Electron mobility is an important electrical parameter that can be used to evaluate whether Al0.2In0.8Sb/InAsxSb1-x quantum well heterostructures grown by MBE can be used to prepare high mobility transistors. As shown in

Fig.12 Electron mobility μ and 2DEG concentrations ns versus different As/In ratios
图12 电子迁移率μ和2DEG浓度ns 与不同As/In比的关系
Based on the previous optimization results, it was found that the thickness of the InAsxSb1-x layer has a significant impact on electron mobility. Therefore, the influence of channel thickness on electron mobility and 2DEG concentration was studied while fixing the Sb/In ratio at 6 and As/In ratio at 3.

Fig.13 Electron mobility μ and 2DEG concentration ns versus different channel thickness
图13 电子迁移率μ和2DEG浓度ns与不同沟道厚度的关系
In summary, the influence of the V/III ratio on the transport properties and crystal quality of the 200 nm InAsxSb1-x thin film and Al0.2In0.8Sb/InAsxSb1-x quantum well heterostructures has been investigated. The calculation results indicated that the Sb component is 0.6 in the InAsxSb1-x thin film when grown under the conditions of Sb/in ratio of 6 and As/in ratio of 3. Meanwhile, the highest electron mobility of InAsxSb1-x thin film measured at room temperature was 28 560 c
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