Characterization of n-n Ge/SiC heterojunction diodes (original) (raw)
Related papers
Journal of Applied Physics
In this article, we report on the physical and electrical nature of Ge/SiC heterojunction layers that have been formed by molecular beam epitaxy ͑MBE͒ deposition. Using x-ray diffraction, atomic force microscopy, and helium ion microscopy, we perform a thorough analysis of how MBE growth conditions affect the Ge layers. We observe the layers developing from independent islands at thicknesses of 100 nm to flat surfaces at 300 nm. The crystallinity and surface quality of the layer is shown to be affected by the deposition parameters and, using a high temperature deposition and a light dopant species, the layers produced have large polycrystals and hence a low resistance. The p-type and n-type layers, 300 nm thick are formed into Ge/SiC heterojunction mesa diodes and these are characterized electrically. The polycrystalline diodes display near ideal diode characteristics ͑n Ͻ 1.05͒, low on resistance and good reverse characteristics. Current-voltage ͑I-V͒ measurements at varying temperature prove that all the layers have two-dimensional fluctuations in the Schottky barrier height ͑SBH͒ due to inhomogeneities at the heterojunction interface. Capacitance-voltage analysis and the SBH size extracted from I-V analysis suggest strongly that interface states are present at the surface causing Fermi-level pinning throughout the bands. A simple model is used to quantify the concentration of interface states at the surface.
Analysis of inhomogeneous Ge/SiC heterojunction diodes
Journal of Applied Physics, 2009
In this article Schottky barrier diodes comprising of a n-n Germanium-Silicon Carbide (Ge-SiC) heterojunction are electrically characterised. Circular transmission line measurements prove that the nickel front and back contacts are ohmic, isolating the Ge/SiC heterojunction as the only contributor to the Schottky behaviour. Current-voltage plots taken at varying temperature (IVT) reveal that the ideality factor (n) and Schottky barrier height (Φ) are temperature dependent and that incorrect values of the Richardson constant (A * *) are being produced, suggesting an inhomogeneous barrier. Techniques originally designed for metal-semiconductor SBH extraction are applied to the heterojunction results to extract values of Φ and A * * that are independent of temperature. The experimental IVT data is replicated using the Tung model. It is proposed that small areas, or patches, making up only 3% of the total contact area will dominate the I-V results due to their low SBH of 1.033 eV. The experimental IVT data is also analysed statistically using the extracted values of Φ to build up a Gaussian distribution of barrier heights, including the standard deviation and a mean SBH of 1.126 eV, which should be analogous to the SBH extracted from capacitance-voltage (C-V) measurements. Both techniques yield accurate values of A * * for SiC. However, the C-V analysis did not correlate with the mean SBH as expected.
The pn Junctions of Epitaxial Germanium on Silicon by Solid Phase Doping
IEEE Transactions on Electron Devices, 2014
Boron and phosphorous layers were deposited by ultrahigh-vacuum chemical vapor deposition at 450°C using B 2 H 6 and PH 3 , respectively, to form the abrupt doping profiles in epitaxial Ge on Si substrate. The diffusion process without ion implantation damage is demonstrated by the nearly ideal diode characteristics for the first time. The Ge diodes doped by the boron layer and the phosphorous layer have the ON/OFF ratio of ∼1×10 5 and ∼1.5×10 5 with the extremely low reverse current densities of ∼1×10 −4 A/cm 2 and ∼4 × 10 −5 A/cm 2 , respectively. The good crystalline quality at junction free from implantation damage by in situ solid phase doping reflects these figures of merit.
High doped MBE Si p–n and n–n heterojunction diodes on 4H-SiC
Microelectronics Journal, 2007
The physical and electrical properties of heavily doped silicon (5 Â 10 19 cm À3 ) deposited by molecular beam epitaxy (MBE) on 4H-SiC are investigated in this paper. Silicon layers on silicon carbide have a broad number of potential applications including device fabrication or passivation when oxidised. In particular, Si/SiC contacts present several atractive material advantages for the semiconductor industry and especially for SiC processing procedures for avoiding stages such as high temperature contact annealing or SiC etching. Si films of 100 nm thickness have been grown using a MBE system after different cleaning procedures on n-type (0 0 0 1) Si face 81 off 4H-SiC substrates. Isotype (n-n) and an-isotype (p-n) devices were fabricated at both 500 and 900 1C using antimonium (Sb) or boron (B), respectively. X-ray diffraction analysis (XRD) and scanning electronic mircorscope (SEM) have been used to investigate the crystal composition and morphology of the deposited layers. The electrical mesurements were performed to determine the rectifiying contact characteristics and band offsets. r
Influence of Annealing Atmosphere on the Characteristics of Ga2O3/4H-SiC n-n Heterojunction Diodes
Materials
Ga2O3/4H-SiC n-n isotype heterojunction diodes were fabricated by depositing Ga2O3 thin films by RF magnetron sputtering. The influence of annealing atmosphere on the film quality and electrical properties of Ga2O3 layers was investigated. X-ray diffraction (XRD) analysis showed a significant increase in the peak intensities of different faces of β-Ga2O3 {(−201), (−401) and (002)}. X-ray photoelectron spectroscopy (XPS) measurement showed that the atomic ratio of oxygen increases under high-temperature annealing. Moreover, an N2-annealed diode exhibited a greater rectifying ratio and a lower thermal activation energy owing to the decrease in oxygen-related traps and vacancies on the Ga2O3 film and Ga2O3–metal interface.
Effect of thermal treatment on the characteristics of iridium Schottky barrier diodes on n-Ge
Iridium (Ir) Schottky barrier diodes were deposited on bulk grown (1 0 0) Sb-doped n-type germanium by using the electron beam deposition system. Electrical characterization of these contacts using current-voltage (I-V) and capacitance-voltage (C-V) measurements was performed under various annealing conditions. The variation of the electrical properties of these Schottky diodes can be attributed to combined effects of interfacial reaction and phase transformation during the annealing process. Thermal stability of the Ir/n-Ge (1 0 0) was observed up to annealing temperature of 500 • C. Furthermore, structural characterization of these samples was performed by using a scanning electron microscopy (SEM) at different annealing temperatures. Results have also revealed that the onset temperature for agglomeration in a 20 nm Ir/n-Ge (1 0 0) system occurs between 600 and 700 • C.
AIP Advances, 2017
The growth, morphological, and electrical properties of thin-film Ge grown by molecular beam epitaxy on Si using a two-step growth process were investigated. High-resolution x-ray diffraction analysis demonstrated ∼0.10% tensile-strained Ge epilayer, owing to the thermal expansion coefficient mismatch between Ge and Si, and negligible epilayer lattice tilt. Micro-Raman spectroscopic analysis corroborated the strain-state of the Ge thin-film. Cross-sectional transmission electron microscopy revealed the formation of 90 • Lomer dislocation network at Ge/Si heterointerface, suggesting the rapid and complete relaxation of Ge epilayer during growth. Atomic force micrographs exhibited smooth surface morphology with surface roughness < 2 nm. Temperature dependent Hall mobility measurements and the modelling thereof indicated that ionized impurity scattering limited carrier mobility in Ge layer. Capacitanceand conductance-voltage measurements were performed to determine the effect of epilayer dislocation density on interfacial defect states (D it) and their energy distribution. Finally, extracted D it values were benchmarked against published D it data for Ge MOS devices, as a function of threading dislocation density within the Ge layer. The results obtained were comparable with Ge MOS devices integrated on Si via alternative buffer schemes. This comprehensive study of directly-grown epitaxial Ge-on-Si provides a pathway for the development of Ge-based electronic devices on Si.
Electrical and optical properties of Ge–implanted 4H–SiC
Applied Physics Letters, 1999
The structural, electronic, and optical properties of single crystalline n-type 4H-SiC implanted with Ge atoms have been investigated through x-ray diffraction ͑XRD͒, Rutherford backscattering spectroscopy ͑RBS͒, Raman spectroscopy, and sheet resistivity measurements. Ge atoms are implanted under the conditions of a 300 keV ion beam energy with a dose of 2ϫ10 16 cm Ϫ2. X-ray diffraction of the Ge-implanted sample showed broadening of the Bragg peaks. A shoulder on the ͑0004͒ reflection indicated an increase in the lattice constant corresponding to substitutional Ge and implantation induced lattice damage, which was repaired through thermal annealing at 1000°C. The diffraction pattern after annealing indicated improved crystal structure and a peak shift to a lower reflection angle of 35.2°. The composition of Ge detected through XRD was reasonably consistent with RBS measurements that indicated 1.2% Ge in a 1600-Å-thick layer near the SiC surface. Raman spectroscopy also showed fundamental differences in the spectra obtained for the Ge-implanted SiC ͑SiC:Ge͒ compared to a pure sample of SiC. Sheet resistivity measurements indicate a higher conductivity in the Ge implant by a factor of 1.94 compared to unimplanted SiC. These results have demonstrated the possibility of substitutional implantation of Ge atoms into the crystalline lattice of 4H-SiC substrates. The change in composition and properties may have numerous electronic device applications including high power, high temperature, optoelectronic, as well as high frequency device structures.
A p-Ge/sub 1-x/C/sub x//n-Si heterojunction diode grown by molecular beam epitaxy
IEEE Electron Device Letters, 2000
We report on the fabrication and characterization of the first p-n diode made from a heterojunction of epitaxial p-type Ge 0:998 C 0:002 on an n-type Si substrate. Epitaxial Ge 0:998 C 0:002 was grown on a (100) Si substrate by solid source molecular beam epitaxy. The p-GeC/n-Si junction exhibits diode rectification. The I-V characteristics of the p-GeC/n-Si diode indicate a reasonable reverse saturation current of 89 pA/m 2 at 01 V and a high reverse breakdown voltage in excess of 040 V. Photoresponse from the Ge0:998C0:002 p-n diode was observed from 1.3-m laser excitation resulting in an external quantum efficiency of 1.4%.
Effect of thermal treatment on the characteristics of iridium Schottky barrier diodes on n-Ge (100)
Journal of Alloys and Compounds, 2012
Iridium (Ir) Schottky barrier diodes were deposited on bulk grown (100) Sbdoped n-type germanium by using the electron beam deposition system. Electrical characterization of these contacts using current-voltage (I-V) and capacitance-voltage (C-V) measurements was performed under various annealing conditions. The variation of the electrical properties of these Schottky diodes can be attributed to combined effects of interfacial reaction and phase transformation during the annealing process. Thermal stability of the Ir/n-Ge (100) was observed up to annealing temperature of 500 o C. Furthermore, structural characterization of these samples was performed by using a scanning electron microscopy (SEM) at different annealing temperatures. Results have also revealed that the onset temperature for agglomeration in a 20 nm Ir/n-Ge (100) system occurs between 600-700 o C.