(Color online) Spectral reflectance for structures T5 and T10 measured with an incident angle of 45 and with a p-polarized source. The inset provides a closer view of the plasmon feature due to the Berreman effect.
(Color online) DIC microscopy images of InAs homoepitaxial layers with different kinds of defects. (a) Structure T1 and the oval defect with a pit; (b) structure T3 and the oval defect without a pit; (c) structure T10 and the truncated pyramid defect; (d) structure T9 and the round defect.
(Color online) Relation between the surface defect density and growth conditions of InAs homoepitaxial layers. A larger circle size shows that the corresponding InAs layer has a smaller defect density. The gray area indicates a transition region that separates regions where 2 × 4 or 4 × 2 reconstructions were observed during growth. The transition region was experimentally determined by decreasing the As flux for a brief time during some of the layer growths. Based on the RHEED patterns, all the structures were grown in the As-stabilized (2 × 4) region except T10.
(Color online) SEM images (a)–(c) captured by an annular backscattered electron detector and 2 × 2 μm2 AFM area scans (d)–(f) of the homoepitaxial structures grown at different conditions. The color scale is 2 nm in the AFM images. The substrate temperature (T), As2/In flux ratio (V/III), RMS surface roughness (RMS), and peak to valley height (P-V) are as follows: (a) and (d) structure T2, T = 405 °C, V/III = 11:1, RMS = 0.22 nm, and P-V = ∼1.3 nm; (b) and (e) structure T6, T = 427 °C, V/III = 14:1, RMS = 0.19 nm, and P-V = ∼0.8 nm; (c) and (f) structure T11 grown at 0.22 ML/s, T = 400 °C, V/III = 8:1, RMS = 0.13 nm, and P-V = ∼0.8 nm.
Detailed morphology of the same defect in images by SEM and AFM. (a)–(c) The images of the same defect at the same scale; (a) and (b) Plan-view SEM images captured by an annular backscattered electron detector and the in-lens secondary electron detector, respectively. (c) A 3 × 3 μm2 AFM scan on the defect. The dashed white line indicates the position of the line profile shown in (d). (d) The profile crossing the center of the pit, which shows that the oval defect rises about 25 nm from the surface and a pit depth of ≥250 nm (tip geometry limited). (e) A vertical height corrected oblique-view SEM image of the defect's cross section obtained by FIB milling at 200 pA with 20 nm steps. A dark feature 540 nm from the surface of the hillock is present in five sequential frames and highlighted by a white circle.
(Color online) 2 × 2 μm2 AFM image of the InAs substrate after oxide desorption. The color scale is 4.6 nm.
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