Li Lianbi

Non-UV Photoelectric Properties of the Ni/n-Si/N+-SiC Isotype Heterostructure Schottky Barrier Photodiode

The energy-band structure and non-ultraviolet photoelectric properties of a Ni/n-Si/N+-SiC isotype heterostructure Schottky photodiode are simulated by using Silvaco-Atlas. There are energy offsets in the conduction and valance band of the heterojunction, which are about 0.09 eV and 1.79 eV, respectively. The non-UV photodiode with this structure is fabricated on a 6H-SiC(0001) substrate. J?V measurements indicate that the device has good rectifying behavior with a rectification ratio up to 200 at 5 V, and the turn-on voltage is about 0.7 V. Under non-ultraviolet illumination of 0.6 W/cm2, the device demonstrates a significant photoelectric response with a photocurrent density of 2.9 mA/cm2 and an open-circuit voltage of 63.0 mV. Non-ultraviolet operation of the SiC-based photoelectric device is initially realized.

SiC based Si/SiC heterojunction and its rectifying characteristics

The Si on SiC heterojunction is still poorly understood, although it has a number of potential applications in electronic and optoelectronic devices, for example, light-activated SiC power switches where Si may play the role of an light absorbing layer. This paper reports on Si films heteroepitaxially grown on the Si face of (0001) n-type 6H-SiC substrates and the use of B2H6 as a dopant for p-Si grown at temperatures in a range of 700–950 °C. X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM) tests have demonstrated that the samples prepared at the temperatures ranged from 850 °C to 900 °C are characterized as monocrystalline silicon. The rocking XRD curves show a well symmetry with FWHM of 0.4339° Omega. Twin crystals and stacking faults observed in the epitaxial layers might be responsible for widening of the rocking curves. Dependence of the crystal structure and surface topography on growth temperature is discussed based on the experimental results. The energy band structure and rectifying characteristics of the Si/SiC heterojunctions are also preliminarily tested.

Island-growth of SiCGe films on SiC

SiCGe ternary alloys have been grown on SiC by hot-wall low-pressure chemical vapour deposition. It has been found that the samples exhibit an island configuration, and the island growth of SiCGe epilayer depends on the processing parameters such as the growth temperature. When the growth temperature is comparatively low, the epilayer has two types of islands: one is spherical island; another is cascading triangular island. With the increase of the growth temperature, the islands change from spherical to cascading triangular mode. The size and density of the islands depend on the growth duration and GeH4 flow-rate. A longer growth time and a larger GeH4 flow-rate can increase the size and density of the island in the initial stage of the epitaxy. In our case, The optimal growth for a high density of uniform islands occurred at a growth temperature of 1100°C for 1-minute growth, with 10 SCCM GeH4, resulting in a narrow size distribution (about 30nm diameter) and high density (about 3.5 × 1010 dots/cm2). The growth follows Stranski– Krastanov mode (2D to 3D mode), both of the islands and the 2D growth layer have face-centred cubic structure, and the critical thickness of the 2D growth layer is only 2.5 nm.

Relaxation of 6H-SiC (0001) Surface and Si Adsorption on 6H-SiC (0001): an ab initio Study*

First-principles calculations are carried out to study the relaxation of 6H-SiC (0001) surface and chemisorption models of Si adatoms on four high-symmetry adsorption sites. The surface results show that Si-termination is the preferred termination of the 6H-SiC(0001) polar surface and is more stable than the C-terminated 6H-SiC(0001) polar surface over a wide range of allowed chemical potentials. Four stable atomic configurations (top, bridge, hcp and fcc) are considered, and the adsorption energies and geometries, Mulliken charge population, and partial density of state (PDOS) properties are analyzed. Adsorption energy results show that the top site is the most stable site. The structural properties of Si adsorption on the SiC (0001) surface shows that increasing stability means decreasing bond lengths. Charge populations analysis and PDOS results imply that there is strong interaction between Si adatoms and 6H-SiC (0001) surface.

I/Q mismatch calibration based on digital baseband

A novel I/Q mismatch calibration technique based on a digital baseband for a direct conversion transmitter is implemented in TSMC 0.13 μm CMOS technology. The proposed technique finishes a calibration task, which only needs a calibration chain to detect mismatches and then transmit them to the digital baseband. Simulation results show that the calibrated errors of the proposed technique are less than 7%. The measurement results indicate the function of the proposed technique is correct, but the performance should be improved further.

First-principles calculations on Si (220) located 6H—SiC (101̄0) surface with different stacking sites

6H—SiC (1010) surface and Si (220)/6H—SiC (1010) interface with different stacking sites are investigated using first-principles calculations. Surface energies of 6H—SiC (1010) (case I, case II, and case III) are firstly studied and the surface calculation results show that case II and case III are more stable than case I. Then, the adhesion energies, fracture toughness values, interfacial energies, densities of states, and electronic structures of Si (220)/6H—SiC (1010) interfaces for three stacking models (AM, BM, and CM) are calculated. The CM model has the highest adhesion energy and the lowest interfacial energy, suggesting that the CM is stronger and more thermodynamically stable than AM and BM. Densities of states and the total charge densities give evidence that interfacial bonding is formed at the interface and that Si—Si and Si—C are induced due to the hybridization of C-2p and Si-3p. Moreover, the Si—C is much stronger than Si—Si at the interface, implying that the contribution of the interfacial bonding mainly comes from Si—C rather than Si—Si.