SiC-based phototransistor with a tunnel MOS emitter

Au/tunnel-thin SiO₂/n-6H-SiC structures have first been fabricated and shown to operate as tunnel MOS emitter phototransistors under reverse bias and UV-irradiation conditions (current gain reached 3-7). This paper contains details of sample preparation, measured device characteristics, and their interpretation     

Super-gain silicon MIS heterojunction emitter transistors

Silicon bipolar transistors are described with common emitter current gains approaching 25 000, believed to be the highest ever reported for a bipolar device. A heterojunction emitter structure based on a tunneling metal-thin insulator-semiconductor (MIS) contact in conjunction with a shallow implanted base region is responsible for this improved performance. The significance of this result lies in the fact that it demonstrates advantages in both the injection efficiency of the emitter and the control of base properties which may lead to improved silicon bipolar transistor performance over a range of applications.     

A simple analytical model of the tunnel MIS emitter Augertransistor

A simple analytical model of the tunnel MIS emitter transistor is developed, taking into account the Auger ionization effect. The proposed model predicts the features of DC performance of this device arising from Auger ionization. This model was then used to compute typical characteristics for an Al/SiO₂/n-Si Auger transistor. Generated DC characteristics are in satisfactory agreement with recently published experimental results     

High-gain bipolar transistors with polysilicon tunnel junction emitter contacts

Experimental measurements of the dc gain as a function of temperature and of emitter-base and collector-base current-voltage characteristics for bipolar transistors with polysilicon contacts to the emitter are reported, dc gains as high as 2000 have been measured in devices for which a thin insulating layer was encouraged to grow between the monocrystalline silicon emitter and the polycrystalline silicon contact layer. This gain is 20 times larger than that for devices in which the insulating film growth was inhibited. It is suggested that, for these particular devices, the polysilicon layer contributes to a contact which is very similar to that of a metal-insulator-semiconductor tunnel junction contact. A model based on this hypothesis is developed and shown to give a good fit to all the experimental data.     

Hydrogen-sensitive silicon tunnel MIS switching diodes

Palladium thin SiO2-n-p⁺silicon switching diodes have been fabricated in which the turn-on voltage changes in proportion to the hydrogen concentration in the ambient gas. In the typical diode operated at 100°C, the switching voltage decreases from 5.1 to 3.6 V for 10 ppm hydrogen in air within 2 min and the off-state disappears for 100 ppm within 30 s. Hydrogen sensitivity is ascribed to the increase of a current gain in two transistor model of the device due to the change in palladium work-function.     

A high-low junction emitter structure for improving silicon solar cell efficiency

A new device structure which is designed to substantially increase the open-circuit voltage and the power-conversion efficiency of p-n junction silicon solar cells is described. The structure differs from the conventional cell structure in that it contains a high-low (H-L) junction in the emitter. Based on numerical solutions of the fundamental Shockley differential equations, efficiency improvements of about 15 percent at AM1 and about 40 percent at 50 suns can be epxected. The improvement at 50 suns results in an efficiency of about 20 percent at 27°C.     

An analytic model for the MIS tunnel junction

A comprehensive analytic model describing current flow in the MIS tunnel junction under steady-state conditions is developed. The tunnel junction is viewed as imposing boundary conditions on the usual set of differential equations governing the electrostatic potential and carrier distributions within the semiconductor. These equations are then solved using the approximation techniques applied in conventional p-n junction theory. Full Fermi-Dirac statistics are used where necessary in the model, and surface states are treated using a Shockley-Read-Hall approach. In computing the band-to-metal tunnel currents, it is assumed that each valley in the conduction band and peak in the valence band can be assigned a single tunneling probability factor describing all transitions between that valley or peak and the metal. On making the above approximations, it is found that the state of the junction is described by two coupled nonlinear algebraic equations, which can be solved by routine iterative techniques. The model is applied to generate current-voltage characteristics for a minority-carrier AI-SiOx- pSi diode, operated both in the dark and as a solar cell, and for a negative barrier AI-SiOx-nSi contact exhibiting photocurrent multiplication. The results obtained are in good agreement with those predicted by more precise numerical methods.     

Amorphous silicon phototransistor on a glass substrate

An amorphous silicon n⁺-i-p⁺-i-n⁺thin-film phototransistor was made on a glass substrate. The p⁺base is very thin (∼ 200 Å) compared with 2000 to 5000 Å of the collector i-layer. Therefore, the emitter current which is induced from the photogenerated flux in the collector i-layer is very high. In addition, hole lifetime (minority carrier in the emitter) and transit time are very short, the device possesses fast rise time and fall time of 30 µs, which is mainly governed by the junction capacitance-resistance charging effect and strays.     

Improvements in current gain and breakdown voltage of silicon MIS heterojunction emitter transistors

Significant improvements in the current gain and in the breakdown voltage of high gain devices are reported for silicon-bipolar transistors. These improvements were obtained by the use of a heterojunction MIS tunneling emitter with the tunneling oxide properties more carefully optimized than in earlier devices. Common-emitter current gains above 3 × 10⁴are reported for devices with a breakdown voltage above 30 V.     

Electric measurement and modelling of the emitter base junction behaviour of VLSI silicon transistor

A knowledge of the gain of the emitter base junction center is of great interest to evaluate several phenomena which occur in VLSI technology. These effects are mainly: —the edge effects of the emitter base junction, —the heavily doped emitter effects (bandgap narrowing)… We develop in this paper a method to measure the internal gain of the VLSI bipolar transistors using a weak avalanche multiplication in the collector. To verify our results we proposed a model which is convenient to use with our devices and consistent by comparison with some previous works. For the tested devices the ratio of the overall gain with the internal gain is about 0.5. Furthermore, the model allows a knowledge of the average intrinsic concentration of the degenerate emitter.     

Sensitive GaAlAs/GaAs wide-gap emitter phototransistor for high current applications

GaAlAs/GaAs bipolar phototransistors involving a wide gap emitter have been fabricated which exhibit high current gain with corresponding external quantum efficiencies of the order of 5000. The devices provide a power switching capability of more than 1 W.     

Microwave properties of silicon junction tunnel diodes grown bymolecular beam epitaxy

The bias dependence of the single-port microwave reflection gain of 15 μm-diameter Si Esaki tunnel diodes, grown by molecular beam epitaxy, was studied as a function of frequency. A simple equivalent circuit accurately modeled the data and yielded the forward-bias junction capacitance, which cannot be obtained by conventional low frequency capacitance-voltage techniques. The diodes were highly-doped step p-i-n junctions and exhibited a peak current density of 16 kA/cm ². The microwave reflection gain and cut-off frequency were 12 dB land 1.6 GHz, respectively, with a speed index (slew rate) of 7.1 V/ns     

Boron-doped silicon film as a recombination layer in the tunnel junction of a tandem solar cell

Boron-doped hydrogenated silicon films with different gaseous doping ratios (B2H6/SiH4) were deposited in a plasma-enhanced chemical vapor deposition (PECVD) system. The microstructure of the films was investigated by atomic force microscopy (AFM) and Raman scattering spectroscopy. The electrical properties of the films were characterized by their room temperature electrical conductivity (σ) and the activation energy (Ea). The results show that with an increasing gaseous doping ratio, the silicon films transfer from a microcrystalline to an amorphous phase, and corresponding changes in the electrical properties were observed. The thin boron-doped silicon layers were fabricated as recombination layers in tunnel junctions. The measurements of the Ⅰ-Ⅴ characteristics and the transparency spectra of the junctions indicate that the best gaseous doping ratio of the recombination layer is 0.04, and the film deposited under that condition is amorphous silicon with a small amount of crystallites embedded in it. The junction with such a recombination layer has a small resistance, a nearly ohmic contact, and a negligible optical absorption.     

硼掺杂硅薄膜及其在叠层电池隧道结中的应用

Boron-doped hydrogenated silicon films with different gaseous doping ratios（B2H6/SiH4） were deposited in a plasma-enhanced chemical vapor deposition（PECVD） system.The microstructure of the films was investigated by atomic force microscopy（AFM） and Raman scattering spectroscopy.The electrical properties of the films were characterized by their room temperature electrical conductivity（σ） and the activation energy（Ea）.The results show that with an increasing gaseous doping ratio,the silicon films transfer from a microcrystalline to an amorphous phase,and corresponding changes in the electrical properties were observed.The thin boron-doped silicon layers were fabricated as recombination layers in tunnel junctions.The measurements of the I-V characteristics and the transparency spectra of the junctions indicate that the best gaseous doping ratio of the recombination layer is 0.04,and the film deposited under that condition is amorphous silicon with a small amount of crystallites embedded in it.The junction with such a recombination layer has a small resistance,a nearly ohmic contact,and a negligible optical absorption.     

Lateral MIS tunnel transistor

A new device structure called the Lateral MIS Tunnel Transistor (LMISTT) is proposed, and its basic features and characteristics are presented. In this device, effects related to the lateral conduction in MIS tunnel structures are implemented. The device is featured by very simple processing, and shows promise in a variety of applications, including very large scale integration high speed IC's.     

A long-wavelength MEMS tunable VCSEL incorporating a tunnel junction

In this letter, we describe the performance of a microelectromechanical system tunable vertical-cavity surface-emitting laser operating at 1550 nm and incorporating a tunnel junction for improved current injection and reduced optical loss. These lasers exhibit single-mode powers greater than 0.28 mW over 10 nm of tuning. Peak single-mode powers are greater than 0.8 mW and minimum threshold currents are less than 1 mA.     

The post-damage behavior of a MOS tunnel emitter transistor

The effect of oxide damage on the characteristics of an Al/SiO₂/n-Si MOS tunnel emitter transistor, is considered. The pre-breakdown oxide degradation is shown to reduce the current gain and to extend the S-shape segment of the collector characteristic of a device. This kind of damage may be formally modeled as an increase of the SiO₂ thickness deviation. After a soft breakdown, the transistor usually loses its bistability and has much lower gain in the range of large currents, while in the low-current mode the device behavior remains almost unchanged. Essential is the size of the zone affected by a breakdown spot, which is, to a great extent, regulated by the conductivity of an inversion layer.     

The SIS tunnel emitter: A theory for emitters with thin interface layers

Silicon n-p-n transistors are made with emitters consisting of a polycrystalline and monocrystalline region with a thin (20-60-Å) "insulating" interfacial layer in between (SIS structure). These transistors show a remarkable increase in emitter efficiency with emitter Gummel numbers up to 7 × 10¹⁴s.cm^-4, and a low positive or even negative temperature coefficient of the current gain. A model is proposed to explain the mechanism in terms of tunneling through the interfacial layer. The electrical characteristics are measured in the temperature range 290-415 K. From the measurements it is deduced that the tunnel probability for holes (Ph) is 10^-2to 10^-3and that for electrons (Pe) is >10^-5. There also exists a band bending of 30-90 mV at the interfaces with the interfacial layer.