GaSb and InAs: New Materials for Metal-Semiconductor Point-Contact Diodes

Metal-semiconductor point contact diodes have proved to be good detectors and mixers for radiation from the far-infrared to visible. Until now GaAs, InSb and InP are the most studied and used semiconductor materials for these devices. In this work we present the performance in the visible and infrared region for metal-semiconductor point-contact diodes with GaSb or InAs as the semiconductor layers. These two new materials have shown good characteristics.     

Frequency measurements of optically pumped far-infrared laser lines

In this work, we report the frequency measurements of optically pumped far-infrared (FIR) laser lines. We use the heterodyne technique of mixing FIR laser radiation and microwave radiation on a metal-insulator-metal (MIM) point contact tunnel diode, to determine the FIR laser frequencies. The two FIR laser systems, consisting of CO₂ waveguide pump lasers and Fabry-Perot FIR laser cavities, and MIM diode were developed by us. To check the system, we have measured some FIR laser line frequencies previously reported in the literature. An average fractional frequency reproducibility of ±7×10^-7, between our measurements and the previous ones, permit us to use our system to measure five new FIR laser frequencies     

Tunneling in field induced diode in indium antimonide

Tunneling in the forward bias polarity of a field induced diode in indium antimonide is treated theoretically and experimentally. The theory leads to tunneling current-voltage characteristics with a region of negative resistance which are dependent upon the various parameters of the device, such as the gate voltage, substrate acceptor concentration and oxide thickness. A three-terminal device in which the gate voltage controls the tunneling I–V characteristics can thus be realized.Measurements were performed on an experimental device obtained by diffusion of cadmium into N-type InSb semiconductor. A chemically deposited SiO₂ layer was used to isolate the evaporated CrAu gate electrode from the substrate. Deviations from theory are shown to result from the two-dimensional character of the device.     

Heterodyne frequency measurements of FIR laser lines around 1.2 and1.6 THz

We present the frequency measurements of 14 far-infrared (FIR) laser lines. We use the heterodyne technique of mixing FIR laser transitions and microwave radiation on a MIM point contact diode to determine the FIR frequencies. The main motivation was to measure the frequency of laser lines of metrological interest, around the 1.6 and 1.2 THz regions. We also present 15 new FIR laser lines we found while performing the frequency measurements, with wavelengths ranging from 90 μm to 819.2 μm. All of them are characterized in wavelength, polarization, intensity, working pressure and absorption offset     

Performance of W-InSb Metal-Semiconductor Point-Contact Diodes as Detectors and Mixers in the Near Infrared

Metal-Insulator-Metal (MIM) and Schottky-barrier diodes have been used extensively in the past years as harmonic generators and mixers for frequency measurements in the spectral range from the far-infrared to the visible. MIM diodes present a very low fabrication cost and are easy to handle, while Schottky diodes are mechanically more stable and long-lived. In the present work we discuss the performance of a metal-semiconductor point-contact diode for the radiation around 1 μm. This device, which may be viewed as a hybrid between a MIM and a Schottky diode, combines the simplicity and easiness of fabrication of the MIM diode with the stability and the long contact life typical of the Schottky diode. It proved to be very efficient even for visible light.     

On the work mechanism of MIM point contact diodes

We have performed systematic measurements on a W-Ni MIM point contact diode at different IR, FIR, and IF frequencies in order to investigate the mechanisms responsible for the different response times observed in the diode operation. Our results led to the experimental confirmation of a second effect of thermal nature, besides tunnel effect, responsible for the diode operation. We measure the cutoff frequency of this second effect, which results in good agreement with our theoretical interpretation.     

高功率高可靠性9XX nm激光二极管

为了提高半导体激光二极管的输出功率和可靠性,通过在有源区两侧势垒层和波导层之间引入高禁带宽度的GaAsP,抑制有源区载流子的泄漏,极大地改善了器件的性能。研究结果表明:在10~40℃温度范围内器件特征温度从原来的150 K提高至197.37 K(-75.76℃),峰值波长随温度的漂移系数为0.207 nm/℃;条宽200μm、腔长2000μm的9XX nm激光二极管可靠性工作的最大输出功率高达14.4 W;器件在注入电流为7 A时取得71.8%的最大电光转换效率,斜率效率为1.21 W/A。器件在恒定电流下的加速老化测试显示激光二极管可靠性工作寿命达2000 h以上。     

Far infrared heterodyne detectors

The characteristics of far infrared detectors are reviewed. Three detectors, the InSb hot electron bolometer, the GaAs Schottky diode and the Josephson point contact junction, have been incorporated as mixers into sensitive heterodyne systems. The performances of existing heterodyne receivers/radiometers are described and compared. Other applications of submillimeter heterodyne techniques are discussed.     

Improved light-output power of GaN LEDs by selective region activation

A novel selective high resistivity region (SHRR) is created under the p-pad metal electrode of a normal GaN light emitting diode. In conventional designs, light generated under the opaque p-pad metal electrode is absorbed or reflected by the contact and lost. In the SHRR design, the area under the p-pad metal electrode is selectively given a higher resistance, reducing current flow and light generation under the contact. Under constant current testing, the current normally passing through the SHRR region is instead distributed over the visible (i.e., useful) area of the device, resulting in significantly increased light-output power and luminous efficiency.     

Low frequency characteristics of a quasioptical Schottky diode detector part II: Experimental results

A detailed experimental study of the low frequency (video) response of a quasioptical Schottky diode detector over the microwave and FIR wavelength range is presented. An optimization of the responsivity versus the bias current is proposed and a generalized curve of the saturation power versus the FIR wavelength is given. This curve defines for any antenna point-contact Schottky diode detector, suitable for FIR detection, the power range for a linear detector response. A simple method is also described to calculate the coupling efficiency of the laser radiation into the antenna reception pattern.     

A low drive voltage,transparent, metal-free n–i–p electrophosphorescent light emitting diode

We demonstrate a transparent, inverted, electrophosphorescent n–i–p organic light emitting diode (OLED) exhibiting a luminance of 500 cd/m² at 3.1 V, and with a luminous power efficiency of 23 lm/W when light emitted from both top and bottom surfaces is summed. We find that 10% more light is emitted from the top surface; hence a power efficiency of 12 lm/W is obtained for a device viewed through the top, transparent contact. This device, with applications to head-up and displays employing n-type Si driver circuitry, has significantly higher power efficiency and lower drive voltage than undoped fluorescent inverted OLEDs. Efficient injection of both electrons and holes is made possible by controlled n- and p-doping of the transport layers with high doping levels. The light emitting region is protected from ITO sputtering damage by a 210 nm thick p-doped hole transport layer. The transparency of the device at the peak OLED emission wavelength of 510 nm is (80 ± 5)%.     

Unbiased InP detectors in the submillimetre wave region

High sensitivity unbiased detectors employing Ni-nInP Schottky-barrier diodes have been developed in a submillimetre-wave region. The voltage sensitivities of 120 V/W at 300 GHz and 17 V/W at 450 GHz were obtained, which are about three times higher than those of the usually used unbiased Si point contact diode detectors.     

Direct observation of the differences between Raman scatering and population inversion transition for their emission frequencies and pulse waveforms

In FIR laser emissions optically by a CO₂ laser, it has been reported that there are two different process namely “induced Raman scattering” and “population inversion transition”. In this paper, we show that the two different process have clearly different characteristics in emission frequensies and pulse waveforms in the case of a TEA-CO₂ laser excitation. We used in this work an intra-cavity etalon for the study of the emission frequensies and also we used a MOM point contact diode for the detection of the wavaformes. Especially, we show that the FIR pulse waveformes are able to analyze numerically on the concept of rate equations. In conclusion, we indicate that molecules would be classified into two categories with regard to optically pumping by a TEA-CO₂ laser. One of them produce mainly Raman scattered emissions, and other produce only the FIR emissions from population inversion transition in spite of high power intensity excitation.     

Heterodyne detection of tunable FIR sidebands

Continuously tunable far infrared (FIR) laser sidebands have been generated in a Schottky diode by nonlinear mixing the radiation from an optically pumped FIR laser operating between 0.6 and 3 THz with that from a microwave source in the 2-4 GHz range. A very sensitive heterodyne detection is adapted to detect the sidebands generated not only at the sum or difference frequency of the two radiations, but also, for the first time in the FIR region, those related to the mixing of the FIR radiation with the second and third harmonics of the microwaves. The high selectivity of the superheterodyne detection allows easy separation of the various sidebands. The global tunability of this system is 2 × 10 GHz for the more powerful FIR emission lines. To demonstrate the tunability of the device absorption signals of several molecules are presented in the whole range of operation of the system (0.6-3 THz) using either direct or lock-in detection techniques.     

Fabrication and characterization of single ZnO microwire Schottky light emitting diodes

ZnO microwires were grown using noncatalytic chemical vapor deposition method. The average diameter of the ZnO microwires were about 30 μm with length of up to 1–1.5 cm. Single ZnO microwire Schottky light emitting diode was fabricated using Au as Schottky contact electrode and using Al as ohmic contact electrode. The current–voltage (I–V) characteristics of Schottky diodes reveal good rectifying behavior. The Schottky barrier height and ideality factor were calculated to be 0.78 eV and 4.3, respectively. Furthermore, distinct electroluminescence with ultraviolet and visible emissions was detected from this device at room temperature.     

Ni,Pd, or Pt as contact materials for GaSb and InSb semiconductors: Phase diagrams

As processing, and even use, of semiconductor devices usually includes the exposure to elevated temperatures, interface reactions often occur, especially during metallization and further heat treatment. It is thus important to understand the corresponding phase equilibria of the involved elements. We present here the phase diagrams of Ni, Pd, and Pt with GaSb and InSb; experimental results in the systems Ga-M-Sb and In-M-Sb (M = Ni, Pd, Pt) are summarized and are discussed in the context of contact chemistry. For GaSb and InSb, it is found that, from a thermodynamic point of view, binary and ternary compounds in equilibrium with the corresponding semiconductor would be the best choice for contact materials as these contacts will remain stable even after long exposure to elevated temperatures.     

CW submillimeter laser action in ethyl chloride

We present ten new far-infrared (FIR) laser lines obtained by optically pumping ethyl chloride by means of a CW waveguide CO₂ laser with a tunability range of 300 MHz. By means of a heterodyne technique and using, as mixing element, a metal-insulator-metal (MIM) point contact diode or a new home built metal-semiconductor diode, we measured the frequency of all these new lines, as well as that of another line, previously reported in literature. With our new lines, the total number of FIR laser lines emitted by ethyl chloride rises to 14; for each of them we give the offset relative to the center frequency of the pumping radiation, the polarization relative to that of the pumping CO₂ laser, the relative intensity, and the optimum operation pressure. Seven of the new lines have frequencies in the 300-512-GHz range and four of them are strong enough to be used in high-field EPR spectroscopy     

A packaged Schottky diode as detector,harmonic mixer,and harmonic generator in the 25–500 GHz range

This paper describes experimental results obtained with a packaged GaAs Schottky barrier diode in contact with a coaxial connector and placed across waveguides for bands Ka, V, E, W or F. Among the microwave sources used for calibration were 9 carcinotrons in the frequency interval 51–490 GHz. As soon as the frequency F is above the waveguide cut-off frequency, the different characteristics do not depend critically on the waveguide size for V, E, W and F bands. The video detection sensitivity, of several 100 mV/mW at 50 GHz and below, decreases as F^?4 in the range 51–500 GHz. Coupling an X-band centimeter frequency via the coaxial connector and a millimeter frequency via the waveguide permits harmonic mixing in the diode. Between 36 and 490 GHz, the harmonic mixing number varies from 3 up to the very large value 40 with conversion losses from 18 to 88 dB. The minimum detectable signal in the 100 kHz band can be as low as ?90 dBm at 80 GHz. A noticeable millimeter power is available at the waveguide output from injected centimeter power by harmonic generation. Starting for instance with 100 mW around 11.5 GHz, we have measured 0.1 mW at 80 GHz and 0.1 μW at 230 GHz. To illustrate the possibility of creating usable millimeter and submillimeter wave without heavy equipment (such as carcinotrons or millimeter klystron) we report spectroscopic experiments in Rydberg atoms. Resonances have been observed up to 340 GHz by harmonic generation (28th harmonic) from an X-band klystron).     

Comparison of the responsivity of W-Ni point contact MBM diodes with W-Si point contact Schottky diodes

The responsivities of the W-Ni point contact MBM diode and the W-Si point contact Schottky diode (commercial 1N23B diode) are compared at 9.5 GHz under identical conditions. The MBM diode has almost half the responsivity of the Schottky diode and was measured to be ≃20 V/W for a 550 Ω termination. The responsivity of the MBM diode decreases with an increase of the frequency. However, this is not due to the RC time constant of MBM diodes, but due to the antenna properties of the whisker and the relaxation behavior of the metallic whisker antenna.     

High-detectivity (>1×1010 cm√Hz/W),InAsSb strained-layer superlattice, photovoltaic infrared detector

A high-detectivity infrared photodiode grown using molecular beam epitaxy (MBE) is discussed. It consisted of a p-`i'-n device embedded in an InAs<sub>0.15</sub>Sb<sub>0.85</sub>/InSb strained-layer superlattice (SLS) with equal 150 Å-thick layers. The SLS was grown on top of a thick, composition-graded In<sub>x</sub>Ga<sub>1-x</sub>Sb (x=1.0-0.9) strain-relief buffer on an InSb substrate. The p- and n-type dopants were Be and Se, respectively. The doping level in the `i' region represents the background doping level in the MBE system. The surface passivated device exhibited detectivities ⩾1×10¹⁰ cm√Hz/W at wavelengths ⩽10 μm. This device demonstrates the feasibility of a long-wavelength, photovoltaic infrared detector technology based on InAsSb SLSs