Low Ideality Factor Research Articles

Over 1 kV Vertical GaN-on-GaN p-n Diodes With Low On-Resistance Using Ammonia Molecular Beam Epitaxy

Vertical GaN-on-GaN p-n diodes grown by ammonia molecular beam epitaxy (NH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> MBE) are reported in this letter for prospective high-power application devices. The diodes, consisting of only 4 μm drift layer with low unintentionalbackgrounddoping of ~ 3×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">15</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> , showed a maximum breakdown voltage of >1.0 kV and a low differential specific on-resistance of 0.28 mΩ-cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Moreover, these diodes exhibited an excellent rectifying behavior with a low minimum ideality factor of 1.36 and a punch-through electric field comparable to the state-of-the-art vertical GaN-on-GaN p-n diodes grown by metalorganic chemical vapor deposition (MOCVD). These results suggest that all-MBE vertical GaN-on-GaN p-n diodes grown by NH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> MBE can be promising for small-size high-power electronic devices.

Record-High-Performance Hydrogenated In-Ga-Zn-O Flexible Schottky Diodes.

High-performance In-Ga-Zn-O (IGZO) Schottky diodes (SDs) were fabricated using hydrogenated IGZO (IGZO:H) at a maximum process temperature of 150 °C. IGZO:H was prepared by Ar + O2 + H2 sputtering. IGZO:H SDs on a glass substrate exhibited superior electrical properties with a very high rectification ratio of 3.8 × 1010, an extremely large Schottky barrier height of 1.17 eV, and a low ideality factor of 1.07. It was confirmed that the hydrogen incorporated during IGZO:H deposition increased the band gap energy from 3.02 eV (IGZO) to 3.29 eV (IGZO:H). Thus, it was considered that the increase in band gap energy (decrease in electron affinity) of IGZO:H contributed to the increase in the Schottky barrier height of the SDs. Angle-resolved hard X-ray photoelectron spectroscopy analysis revealed that oxygen vacancies in IGZO:H were much fewer than those in IGZO, especially in the region near the film surface. Moreover, it was found that the density of near-conduction band minimum states in IGZO:H was lower than that in IGZO. Therefore, IGZO:H played a key role in improving the Schottky interface quality, namely, the increase of Schottky barrier height, decrease of oxygen vacancies, and reduction of near-conduction band minimum states. Finally, we fabricated a flexible IGZO:H SD on a poly(ethylene naphthalate) substrate, and it exhibited record electrical properties with a rectification ratio of 1.7 × 109, Schottky barrier height of 1.12 eV, and ideality factor of 1.10. To the best of our knowledge, both the IGZO:H SDs formed on glass and poly(ethylene naphthalate) substrates achieved the best performance among the IGZO SDs reported to date. The proposed method successfully demonstrated great potential for future flexible electronic applications.

Performance improvement of n-TiO2/p-Si heterojunction by forming of n-TiO2/polyphenylene/p-Si anisotype sandwich heterojunction

The n-TiO2/polyphenylene (PPh)/p-Si heterojunction devices were fabricated in which PPh film and TiO2 top layer were grown on p-Si substrates by diazonium modification method and cathodic electrodeposition, respectively. The XPS, UV–vis diffuse reflectance and STM analyses of the films were performed. After the characterization of deposited films and the fabrications of n-TiO2/PPh/p-Si sandwich devices, the electrical measurements of nine devices were carried out from the current–voltage (I–V) characteristics, at room temperature. The I–V characteristics of n-TiO2/PPh/p-Si heterojunctions were compared with TiO2/p-Si heterojunctions, one of them was analysed in more detailed and it was observed that the n-TiO2/PPh/p-Si gave better performance than TiO2/p-Si heterojunctions such that lower ideality factor, higher rectification ratio and more stable reverse current characteristics. Then, the main device parameters of n-TiO2/PPh/p-Si were compared with many devices reported in literature based on TiO2/p-Si device and TiO2 preparation techniques. Furthermore, the rectification ratio of n-TiO2/PPh/p-Si heterojunction was 9.42 × 105, while it was 5.80 × 102 for TiO2/p-Si heterojunction. Later, the capacitance-voltage (C–V) and conductance-voltage (G-V) measurements of the n-TiO2/PPh/p-Si heterojunction was performed depending on applied frequency and bias and it was observed that the values of capacitance and conductance were found a strongly function of bias voltage.

High Photoresponsive p-Si/n-In2O3 Junction Diodes with Low Ideality Factor Prepared Using Closely Packed Octahedral Structured In2O3 Thin Films

Octahedral indium oxide thin films with different precursor concentrations of 0.05, 0.075, 0.1 and 0.125 M were coated on glass substrates at 450 °C using jet nebulizer spray pyrolysis technique. Surface morphology of the prepared samples showed closely packed octahedrons for all concentrations. The measured root-mean-square value of the films was varied between 40.45 and 188.98 nm with increased precursor concentrations. From optical analysis, the calculated optical band gap was continuously decreased with increase in precursor concentrations. A slight blue shift was recorded through the PL spectrum while increasing the precursor concentration due to the oxygen vacancies. The nature of electrical conductivity of the In2O3 films was analysed. Interestingly, we have calculated two types of activation energies in the In2O3 films one is corresponding to low temperature and another is higher temperature. Further, p-Si/n-In2O3 junction diodes are fabricated with different precursor concentrations. Particularly, the 0.075 M of p-Si/n-In2O3 junction diode recorded a minimum ideality factor of n = 2.64 under light exposed condition, confirming the photo-conducting nature of the diodes in visible wavelength range.

Quasi-Vertical GaN Schottky Barrier Diode on Silicon Substrate With 1010 High On/Off Current Ratio and Low Specific On-Resistance

In this letter, we report a quasi-vertical GaN Schottky barrier diode (SBD) fabricated on a hetero-epitaxial layer on silicon with low dislocation density and high carrier mobility. The reduction of dislocation is realized by inserting a thin layer with high density of Ga vacancies to promote the dislocation bending. The dislocation density is ${1.6}\times {10}^{{8}}$ cm−2 with a GaN drift layer thickness of $4.5~\mu \text{m}$ . The fabricated prototype GaN SBD delivers a high on/off current ratio of $10^{{10}}$ , a high forward current density of 1.6 kA/cm2@3 V, a low specific on-resistance of 1.1 $\text{m}\Omega \cdot \text {cm}^{{2}}$ , and a low ideality factor of 1.23.

Improved performance of AlGaInP red micro-light-emitting diodes with sidewall treatments.

The electrical and optical improvements of AlGaInP micro-light-emitting diodes (µLEDs) using atomic-layer deposition (ALD) sidewall passivation were demonstrated. Due to the high surface recombination velocity and minority carrier diffusion length of the AlGaInP material system, devices without sidewall passivation suffered from high leakage and severe drop in external quantum efficiency (EQE). By employing ALD sidewall treatments, the 20×20 µm2 µLEDs resulted in greater light output power, size-independent leakage current density, and lower ideality factor. The forward current-voltage characteristic was enhanced by using surface pretreatment. Furthermore, ALD sidewall treatments recovered the EQE of the 20×20 µm2 devices more than 150%. This indicated that AlGaInP µLEDs with ALD sidewall treatments can be used as the red emitter for full-color µLED display applications.

Influence of Crystallographic Orientation on Schottky Barrier Formation in Gallium Oxide

Highly rectifying graphite/I²-Ga2O3 Schottky junctions have been prepared by a simple low-cost drop-casting process. The influence of two different crystal orientations on the current transport mechanism in the graphite-based Schottky junctions was investigated by direct-current (DC) and alternating-current (AC) electrical measurements. The nonideal behavior observed for both $$ \left\langle {\bar{2}01} \right\rangle $$ and $$ \left\langle {010} \right\rangle $$ crystallographic orientations can be explained by the lateral inhomogeneity of the junction related to the imperfection of the graphite/semiconductor interface. A lower density of interface states and their shorter time constants are reported for Schottky junctions formed on $$ \left\langle {\bar{2}01} \right\rangle $$ crystallographic plane, as reflected also by the higher effective barrier height and lower ideality factor.

Beveled Fluoride Plasma Treatment for Vertical $\beta$ -Ga2O3Schottky Barrier Diode With High Reverse Blocking Voltage and Low Turn-On Voltage

In this letter, we report on demonstrating a high performance vertical $\beta $ -Ga2O3 Schottky barrier diode (SBD) based on a self-aligned beveled fluorine plasma treatment (BFPT) edge termination structure. Owing to the strong electronegativity of fluorine ions, the fixed negative charges introduced by F ions during self-aligned BFPT process alleviate the electric field crowding, reduce the reverse leakage current and improve the breakdown voltage up to 1 050V even with a low differential on resistance of 2.5 $\text{m}\Omega \cdot $ cm2, combining with a high $I_{\text {on}}/I_{\text {off}}$ of 109, a Schottky barrier height of 1.03 eV and a low ideality factor of 1.07-1.11.Without implantation and post annealing, the self-aligned BFPT can serve as a simple, effective and viable edge termination technique to fabricate high performance $\beta $ -Ga2O3 rectifiers.

Electrical properties of nitric acid and DMSO treated PEDOT:PSS/n‐Si hybrid heterostructures for optoelectronic applications

ABSTRACTOrganic/inorganic heterostructures are an emerging and interesting field of research for optoelectronics. In this work, an efficient organic/inorganic hybrid heterojunction between PEDOT:PSS and n‐type Silicon has been fabricated for optoelectronic applications. Samples with varying thickness of PEDOT:PSS were prepared by spin coating technique and the electrical conductivity of organic layers was modified using DMSO as additive. Post fabrication, the hybrid heterostructures were treated with HNO3 vapor so as to enhance the conductivity of the organic layer. Surface treatment with HNO3 was found to lower the roughness of the organic layer and enhance the transparency of the layer. I–V characteristics reveal optimized behavior of HNO3 treated PEDOT:PSS layer with a low Ideality factor (n~3.2) and a barrier height (ΦB) of 0.8 eV. The findings of the study provide a promising efficient method to enhance the electrical and device properties of PEDOT:PSS/n‐Si heterostructures for optoelectronic applications. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48952.

(Invited) Electrical Properties of (100) β-Ga2O3 Schottky Diodes with Four Different Metals

Due to its large bandgap (~4.6-4.8 eV), wide range of n-type doping, and single-crystal wafer availability, β-Ga2O3 holds promise for high-efficiency power devices. R&D of β-Ga2O3 has been conducted in Japan for more than a decade; however, funded research programs on this semiconductor material began in the U.S. only five years ago, highlighting its early stage of development. Device development of a semiconductor technology requires the ability to produce suitable ohmic and rectifying (Schottky) contacts. Whereas ohmic and Schottky contacts have been demonstrated on n-type β-Ga2O3, certain characteristics of contacts to β-Ga2O3 differ from contacts to other wide bandgap semiconductors. For example, we found that morphology was problem with many ohmic contact metals, and it was concluded that metal work function is not a dominant predictive factor for forming an ohmic contact to β-Ga2O3 [1]. Furthermore, thermal instability of the standard ohmic contact metallization (Ti/Au) is a concern for operation of devices at elevated temperatures. Schottky contacts to β-Ga2O3 have shown dependence on the orientation, growth method, and choice of metal. For example, on (-201) β-Ga2O3 Schottky barrier heights calculated from I-V measurements were typically between 0.9 and 1.3 eV and displayed little dependence on the metal work function [2]. Our preliminary measurements of selected metals on (100) β-Ga2O3 substrates yielded lower ideality factors and a correlation between barrier height and metal workfunction. The results for Schottky contacts on the (100) surface show some similarities to those previously reported on the (010) surface. In this presentation specific examples of ohmic and Schottky contact metallizations to β-Ga2O3 will provide a platform for more detailed discussion. [1] Y. Yao, R.F. Davis, and L.M. Porter, J. Electron. Mater. 46(4), 2053-2060 (2016). [2] Y. Yao, R. Gangireddy, J. Kim, K. Das, R.F. Davis, and L.M. Porter, J. Vac. Sci. Technol. B 35(3), 03D113.1-7 (2017).

Ultraviolet detection by Cr doped In 2 O 3 TF

Synthesis of indium (III) oxide (In 2 O 3 ) and chromium (Cr)-doped In 2 O 3 thin film (TF) by spin-on technique was reported. The device showed the Schottky nature under dark and light illumination condition. The ideality factor of the diode showed an exponential increase with the decrease in temperature. The low ideality factor of ~4 was calculated at 300 K. The barrier height of the device increased with temperature. The Cr-doped In 2 O 3 TF device possessed high sensitivity compared with undoped In 2 O 3 TF at -2 V all over the temperature range from 10 to 300 K. The Cr-doped In 2 O 3 TF-based device showed extremely high sensitivity toward ultraviolet (320 nm) light as compared with visible light.

Asymmetric Double‐Gate β‐Ga2O3 Nanomembrane Field‐Effect Transistor for Energy‐Efficient Power Devices

AbstractThe ultra‐wide bandgap and cost‐effective melt‐growth of β‐Ga2O3 ensure its advantages over other wide bandgap materials, and competitive electrical performance has been demonstrated in various device structures. In this paper, an asymmetric double‐gate (ADG) β‐Ga2O3 nanomembrane field‐effect transistor (FET) comprised of a bottom‐gate (BG) metal‐oxide field‐effect transistor and a top‐gate (TG) metal‐semiconductor field‐effect transistor (MESFET) is demonstrated. Schottky contact properties are validated by characterizing the lateral Schottky barrier diode (SBD), which exhibits high rectification ratio and low ideality factor. The top‐gate β‐Ga2O3 MESFET shows reasonable electrical performance with a high breakdown voltage, as anticipated by three terminal off‐state breakdown measurement. These properties are further enhanced by double‐gate operation, and superior device performance is demonstrated; positive‐shifted threshold voltage and reduced subthreshold slope enable the asymmetric double‐gate β‐Ga2O3 FET to operate at low power, and almost twice as much transconductance is demonstrated for high‐frequency operation. These results show the great potential of asymmetric double‐gate β‐Ga2O3 FETs for energy‐efficient high‐voltage and ‐frequency devices with optimal material and structure co‐designs.

Structural, optical and electrical properties of the fabricated Schottky diodes based on ZnO, Ce and Sm doped ZnO films prepared via wet chemical technique

In this study, we fabricated Schottky diode devices on ZnO, Sm and Ce doped and co-doped ZnO thin films grown by the sol–gel spin coating. The structural and optical properties of the sol–gel films are studied, and the electrical characteristics of the Schottky diodes are investigated. The crystalline structure and surface morphology were studied using x-ray diffraction and scanning electron microscopy, respectively. Photoluminescence spectroscopy of all films measured at room temperature showed that the UV emission peak was composed of two peaks located at 388 and 405 nm and no visible light emission was detected. UV–vis study revealed that the optical band gap of ZnO decreased after doping. Room temperature I–V characterization revealed a rectification behaviour of all samples. The Schottky diodes fabricated on (Sm and Ce) co-doped ZnO manifest device properties with good rectification (six orders of magnitude), low ideality factor (1.62) and barrier height of 0.82 eV.

Optimal Performance Emulation of PSCs using the Elephant Herd Algorithm Associated with Experimental Validation

Photovoltaics (PVs) are among the most promising low-cost energy sources with high possibility of large-scale solar cell manufacturing and production. Perovskite solar cells (PSCs) are considered as the fore front of third generation of PVs. They are fabricated using solution processes and their power conversion efficiency now exceeds 25%, making them a very attractive alternative to the silicon based devices (amorphous and crystalline). The presence of humidity and oxygen in these cells leads to large degree of nonlinearity that affects their operation mechanisms, hysteresis phenomena, photovoltaic performance and stability. To face these issues, it is important to find the accurate PSCs models and their optimum parameters for assessing their performance. In this paper, three electrical models, single-, double- and triple-diode models, are developed for two types of PSCs and their parameters are optimally extracted using elephant herd optimization (EHO) paradigm. The simulation results have proved the EHO superiority compared with the competitive algorithms and confirmed a high similarity between the estimated parameters with the experimental ones. The proposed three diode model was able to effectively simulate via the EHO algorithm the electrical behavior of perovskite solar cells and confirmed that dye sensitization of the titania compact layer leads to higher performance expressed in terms of low series resistance, high shunt resistance, low diode ideality factor, low diode saturation current, and high open circuit voltage values.

Improved performance of Al/n&lt;sup&gt;+&lt;/sup&gt;Ge Ohmic contact andGe n&lt;sup&gt;+&lt;/sup&gt;/p diode by two-step annealing method

Silicon based germanium devices are crucial parts of optoelectronic integration as CMOS feature size continuously decreases. Germanium has attracted increasing attention due to its higher electron and hole mobility, larger optical absorption coefficient as well as lower processing temperature than those of silicon. However, the high diffusion coefficient and low solid solubility about n-type dopant and relatively high thermal budget required for high n-type doping in Ge make it difficult to achieve high activation n-type doping and excellent n&lt;sup&gt;+&lt;/sup&gt;/p shallow junction for source/drain in the nano-scaled n-MOSFET (here MOSFET stands for). The high activation concentration and shallow junction n-type doping in Ge are greatly beneficial to the scaled Ge n-MOSFET technology. In this work, the ohmic contact of Al/n&lt;sup&gt;+&lt;/sup&gt;Ge and Ge n&lt;sup&gt;+&lt;/sup&gt;/p junction fabricated by a combination of low temperature pre-annealing process and excimer laser annealing for phosphorus-implanted germanium are demonstrated. Prior to excimer laser annealing, the samplesare annealed at a relatively low temperature, which can heal the implantation damages preliminarily. Through the optimization of pre-annealing temperature and time, the low temperature pre-annealing step can play a critical role in annihilating the implantation damages and significantly suppressing phosphorus diffusion in the laser annealing process, resulting in a very small dopant diffusion length at a high activation level of phosphorus. Through the combination of ion implantation and two-step annealing technology, the specific contact resistivity (&lt;i&gt;ρ&lt;/i&gt;&lt;sub&gt;C&lt;/sub&gt;) of Al/n&lt;sup&gt;+&lt;/sup&gt;Ge Ohmic contact is measured by CTLM structure. The optimized annealing condition is 400 &lt;sup&gt;o&lt;/sup&gt;C-10 min of low temperature annealing and 150 mJ/cm&lt;sup&gt;2&lt;/sup&gt; of ELA. Under that annealing condition, the ρ&lt;sub&gt;C&lt;/sub&gt; of the sample by two-step annealing is reduced to 2.61 × 10&lt;sup&gt;–6&lt;/sup&gt; Ω·cm&lt;sup&gt;2&lt;/sup&gt;, which is one order of magnitude lower than that by ELA alone (about 3.44 × 10&lt;sup&gt;–4&lt;/sup&gt; Ω·cm&lt;sup&gt;2&lt;/sup&gt;). The lower value of &lt;i&gt;ρ&lt;/i&gt;&lt;sub&gt;C&lt;/sub&gt; for the sample with LTPA can contribute to the higher carrier concentration and better crystalline quality thanthat without LTPA, which is confirmed by SRP and TEM. Moreover, the rectification ratio of Ge n&lt;sup&gt;+&lt;/sup&gt;/p junction diode is improved to 8.35 × 10&lt;sup&gt;6&lt;/sup&gt; at ± 1 V, which is two orders of magnitudes higher than that by ELA alone. And a lower ideality factor of about 1.07 is also obtained than that by ELA alone, which indicates that the implantation damages can be repaired perfectly by two-step annealing method.

Barrier Inhomogeneity of Schottky Diode on Nonpolar AlN Grown by Physical Vapor Transport

An aluminum nitride (AlN) Schottky barrier diode (SBD) was fabricated on a nonpolar AlN crystal grown on tungsten substrate by physical vapor transport. The Ni/Au-AlN SBD features a low ideality factor n of 3.3 and an effective Schottky barrier height (SBH) of 1.05 eV at room temperature. The ideality factor n decreases and the effective SBH increases at high temperatures. The temperature dependences of n and SBH were explained using an inhomogeneous model. A mean SBH of 2.105 eV was obtained for the Ni-AlN Schottky junction from the inhomogeneity analysis of the current-voltage characteristics. An equation in which the parameters have explicit physical meanings in thermionic emission theory is proposed to describe the current-voltage characteristics of inhomogeneous SBDs.

AlN passivation effect on Au/GaN Schottky contacts

Surface passivation effect with an aluminum nitride (AlN) thin film deposited by atomic layer deposition (ALD) on metal/gallium nitride (GaN) junctions were investigated using current–voltage and capacitance–voltage (CV) measurements. The sample with an AlN layer revealed higher barrier height and lower ideality factor compared to the sample without AlN layer. X-ray photoelectron spectroscopy measurement on bare GaN surface showed the presence of native oxide on the GaN surface. From CV measurements, it was found that the interface state density was reduced with an AlN layer. Hence, deposition of AlN layer by ALD can be used to improve the interface quality of metal/GaN junction.

Numerical Analysis to Determine Reliable One-Diode Model Parameters for Perovskite Solar Cells

With the aim to determine the photo-generated current, diode saturation current, ideality factor, shunt, and series resistances related to the one-diode model for p-i-n planar perovskite solar cells, reference cells with active area of approximately 1 cm2 and efficiencies ranging between 4.6 and 12.2% were fabricated and characterized at standard test conditions. To estimated feasible parameters, the mean square error between the I-V curve data of these cells and the circuital model results were minimized using a Genetic Algorithm combined with the Nelder-Mead method. When considering the optimization process solutions, a numerical sensitivity analysis of the error as a function of the estimated parameters was carried out. Based on the errors behavior that is showed graphically through maps, it was demonstrated that the set of parameters estimated for each cell were reliable, meaningful, and realistic, and being related to errors lower than 9.1 × 10−9. Therefore, these results can be considered as global solutions of the optimization process. Moreover, based on the lower errors obtained from the optimization process, it was possible to affirm that the one-diode model is suitable to model the I-V curve of perovskite solar cells. Finally, the estimated parameters suggested that the average ideality factor is close to 2 when the fill factor of the I-V curves is higher than 0.5. Lower fill factors corresponded to ideality that was higher than 3, linked to lower efficiencies, and high loses effects reflected on lower shunt resistances. Lower ideality factor of 1.4 corresponds to the best performing solar cells.

Effect of growth techniques on the structural, optical and electrical properties of indium doped TiO2 thin films

We have investigated the effect of the growth techniques on the structural, the electrically and optically active defects in Indium doped TiO2 thin films grown by pulsed laser deposition (PLD) and sputtering techniques. X-ray diffraction (XRD) and Raman spectroscopy patterns revealed both rutile and anatase phases for the sputtering samples. On the other hand, only the anatase phase was observed for the PLD samples. The photoluminescence (PL) spectra have unveiled several peaks which were explained by defect related optical transitions. Particularly, the PL bands are fully consistent with anatase/rutile TiO2 phases and the formation of In2O3 during the preparation of our samples. It was also observed that at −4 V reverse bias, the PLD samples have lower leakage currents (∼1.4 × 10−7 A) as compared to the sputtering samples (∼5.9 × 10−7 A). In addition, the PLD samples exhibited lower ideality factors and higher barrier heights as compared to those grown by sputtering. Finally, the Deep Level Transient Spectroscopy (DLTS) measurements have shown only one defect in the PLD samples whereas five defects have been detected in the sputtering samples. Therefore, our results provide strong evidence that the PLD technique is better suited for the growth of In-doped TiO2 thin films.

Interface characteristics and electrical transport of Ge/Si heterojunction fabricated by low-temperature wafer bonding

We report a promising method for oxide-layer-free germanium (Ge)/silicon (Si) wafer bonding based on an amorphous Ge (a-Ge) intermediate layer between Si and Ge wafers. The effect of the exposure time (te), during which the a-Ge is exposed to the air after sputtering and being taken out of the chamber on the bubble density at the bonded interface, is identified and a near-bubble-free Ge/Si bonded interface is achieved for the te of 3 s. The crystallization of a-Ge at Ge/Si bonded interface starts from a-Ge/Ge interface and it fully turns to be single-crystal Ge after post-annealing. The oxide layer at a-Ge/a-Ge bonded interface formed by the interface hydrophilic reaction disappears due to the atom redistribution triggered by the crystallization of a-Ge. As expected, the performance of the Ge/Si heterojunction diode is significantly improved by this oxide-layer-free Ge/Si bonded interface. A low dark current of 1.6 µA, high on/off current ratio of 3.4 × 105, and low ideality factor of 1.02 (150 K) is achieved at −0.5 V for the bonded Ge/Si diode. Finally, the carrier transport mechanisms at Ge/Si bonded interface annealed at different temperatures are also clearly clarified.