High-quality Homoepitaxial Growth Research Articles

High crystalline quality homoepitaxial Si-doped β-Ga2O3(010) layers with reduced structural anisotropy grown by hot-wall MOCVD

A new growth approach, based on the hot-wall metalorganic chemical vapor deposition concept, is developed for high-quality homoepitaxial growth of Si-doped single-crystalline β-Ga2O3 layers on (010)-oriented native substrates. Substrate annealing in argon atmosphere for 1 min at temperatures below 600 °C is proposed for the formation of epi-ready surfaces as a cost-effective alternative to the traditionally employed annealing process in oxygen-containing atmosphere with a time duration of 1 h at about 1000 °C. It is shown that the on-axis rocking curve widths exhibit anisotropic dependence on the azimuth angle with minima for in-plane direction parallel to the [001] and maximum for the [100] for both substrate and layer. The homoepitaxial layers are demonstrated to have excellent structural properties with a β-Ga2O3(020) rocking curve full-widths at half-maximum as low as 11 arc sec, which is lower than the corresponding one for the substrates (19 arc sec), even for highly Si-doped (low 1019 cm−3 range) layers. Furthermore, the structural anisotropy in the layer is substantially reduced with respect to the substrate. Very smooth surface morphology of the epilayers with a root mean square roughness value of 0.6 nm over a 5 × 5 μm2 area is achieved along with a high electron mobility of 69 cm2 V−1 s−1 at a free carrier concentration n=1.9×1019 cm−3. These values compare well with state-of-the-art parameters reported in the literature for β-Ga2O3(010) homoepitaxial layers with respective Si doping levels. Thermal conductivity of 17.4 Wm−1K−1 is determined along the [010] direction for the homoepitaxial layers at 300 K, which approaches the respective value of bulk crystal (20.6 Wm−1K−1). This result is explained by a weak boundary effect and a low dislocation density in the homoepitaxial layers.

Nanoscale selective-area epitaxial growth of Si using an ultrathin SiO2/Si3Ni4 mask patterned by an atomic force microscope

We report selective epitaxial growth of Si using an ultrathin bilayer mask. The key feature of this process is direct writing of nanoscale patterns by means of local anodic oxidation of a Si3N4 layer using an atomic force microscope operated in air. Windows for selective growth are defined by wet etching of the locally oxidized regions. High growth selectivity upon chemical vapor deposition of Si is accomplished by employing the bilayer mask structure which is formed by oxidizing the Si3N4 surface and then selectively desorbing SiO2 in the windows. High-quality homoepitaxial growth is verified by transmission electron microscopy. We also report a simple plasma-treatment technique which solves the problem of retarded SiO2 desorption in the nanoscale windows.

Low-temperature homoepitaxial growth on Si(111) through a Pb monolayer

A monolayer of Pb mediates high-quality homoepitaxial growth on Si (111) surfaces at temperatures where growth with other overlayer elements or on bare surfaces leads to amorphous or highly defective crystalline films. Nearly defect-free epitaxy proceeds for film thicknesses up to 1000 Å with no sign that this is an upper limit. The minimum temperature for high-quality epitaxy depends on the substrate miscut. For a 0.2° miscut, the minimum temperature is 340 °C. Films grown on substrates miscut 2.3° towards [112̄] show good crystalline quality down to 310 °C.

Step-controlled epitaxy of SiC: High-quality homoepitaxial growth

Abstract Chemical vapor deposition (CVD) of silicon carbide (SiC) on off-oriented SiC{0001} substrates (step-controlled epitaxy) is reviewed. In step-controlled epitaxy, surface steps on off-oriented SiC{0001} substrates serve as a template which forces the replication of substrate polytype in the epilayer, and thereby homoepitaxy is realized. High quality of SiC epilayers has been elucidated through optical and electrical characterization. The background doping level could be reduced down to less than 1 × 10 14 cm −3 , and a high electron mobility of 851 cm 2 V −1 s −1 was obtained. Excellent doping controllability over a wide range has been achieved by in-situ doping of a nitrogen donor and an aluminum acceptor. High-voltage (greater than 1 kV) Schottky barrier diodes with low specific on-resistances (less than 5 mωcm −2 ) have been demonstrated by utilizing high-quality epilayers.

ZnSe homo-epitaxial growth by molecular beam epitaxy

High-quality undoped ZnSe homo-epitaxial growth by molecular beam epitaxy was demonstrated. A chemical etchant H2O2, NH4OH and H2O, combined with a new thermal cleaning process, has been found promising for obtaining good initial ZnSe substrate surfaces necessary for high-quality homo-epitaxial growth by molecular beam epitaxy. The photoluminescence (PL) result is compared to that of a hetero-epitaxial layer on GaAs (001) substrate. A free excitonic PL emission line has been distinctly observed on the homo-epitaxial ZnSe layer grown on (001) substrate. A dominant emission line I2 in the 4.2 K PL spectrum of the homo-epitaxial ZnSe layer has been ascribed to In donors introduced by the In solder used to adhere the substrate to the molybdenum holder.