6H-SiC p+-n junctions fabricated by berylliumimplantation

The use of beryllium (Be) as an alternate p-type dopant for implanted silicon carbide (SiC) p⁺-n junctions is experimentally demonstrated. The implanted layers have been characterized with photoluminescence (PL) as well as secondary ion mass spectrometry (SIMS) measurements. In comparison with boron implanted p ⁺-n junctions, Be-implanted junctions show improvement in the forward characteristics while exhibiting slightly higher reverse leakages. The activation energies extracted from the forward conduction and reverse leakage characteristics of the Be-diodes are 1.5 eV, and 0.13 eV, respectively. Moreover, activation energy extraction in the forward ohmic region reveals the Be impurity level at 0.38±0.04 eV. The minority carrier lifetime extracted from reverse recovery measurements is as high as 160 ns for the Be-diodes compared to 82 ns obtained for the B-diodes     

Avalanche multiplication noise characteristics in thin GaAs p+-i-n+ diodes

Avalanche noise measurements have been performed on a range of homojunction GaAs p⁺-i-n⁺ and n⁺-i-p ⁺ diodes with “i” region widths, ω from 2.61 to 0.05 μm. The results show that for ω⩽1 μm the dependence of excess noise factor F on multiplication does not follow the well-established continuous noise theory of McIntyre [1966]. Instead, a decreasing noise factor is observed as ω decreases for a constant multiplication. This reduction in F occurs for both electron and hole initiated multiplication in the thinner ω structures even though the ionization coefficient ratio is close to unity. The dead-space, the minimum distance a carrier must travel to gain the ionization threshold energy, becomes increasingly important in these thinner structures and largely accounts for the reduction in noise     

A comparison between N+-P-P+and P+-N-N+silicon IMPATT diodes

A one-dimensional large-signal computer program that incorporates the material parameters of Si in an exact manner has been employed to compare the efficiency, power output, and other important operating characteristics of both complementary structures of Si IMPATT diodes. The results presented here differ greatly from those already reported by other authors.     

20-GHz high-power GaAs DDR-IMPATT diodes with a p+-p-n-n+structure

GaAs DDR (double-drift-region)-IMPATT diodes have been made by using epitaxial wafers with a p⁺-p-n-n⁺structure, which was made by successive liquid-phase epitaxy of p⁺, p, and n layers on n⁺substrate in one heat cycle. On the diodes with copper heat sink, the maximum CW output power of 1.2 W was obtained at 21 GHz with the efficiency of 15.6 percent.     

Near state-of-the-art power in p+-n-n+D-band IMPATT diode on a wafer with ramped n-n+interface

Fabrication of near state-of-the-art (P0= 110 mW, η = 4.85 percent p⁺-n-n⁺D band (f = 124 GHz) Si IMPATT diode on a wafer with ramped n-n⁺interface is described. Introduction of a critical annealing step, prior to p⁺diffusion, in the fabrication sequence of the diode has been found to yield the above results. Possible reasons for power and efficiency enhancement has been discussed.     

Improved performance of IMPATT diodes fabricated from Ge

Recent results with germanium IMPATT diode oscillators are reported. Both n-p-i-p⁺and n-p structures have shown noise figures of 30 ± 1 dB when operated as amplifiers under high gain conditions in the 8 to 10 GHz range. This represents an approximate 10-dB improvement over comparable Si devices. Power outputs of 30 mW at 3 percent efficiency and 250 mW at 6 percent efficiency were measured for the n-p-i-p⁺and n-p structures, respectively.     

Experimental determination of electron drift velocity in 4H-SiC p+-n-n+ avalanche diodes

4H-SiC p⁺-n-n⁺ diodes of low series resistivity (<1×10^-4 Ω·cm²) were fabricated and packaged. The diodes exhibited homogeneous avalanche breakdown at voltages U_b=250-270 V according to the doping level of the n layer. The temperature coefficient of the breakdown voltage was measured to be 2.6×10^-4 k^-1 in the temperature range 300 to 573 K. These diodes were capable of dissipating a pulsed power density of 3.7 MW/cm² under avalanche current conditions. The transient thermal resistance of the diode was measured to be 0.6 K/W for a 100-ns pulse width, An experimental determination of the electron saturated drift velocity along the c-axis in 4H-SIC was performed for the first time, It was estimated to be 0.8×10⁷ cm/s at room temperature and 0.75×10⁷ cm/s at approximately 360 K     

Passivated millimeter-wave silicon IMPATT diodes fabricated by ion implantation

Ion implantation has been combined with planar-mesa processing techniques to realize a passivated silicon IMPATT diode for millimeter-wavelength operation. A continuous-wave output power of 100 mW was obtained at 62 GHz from a fully passivated single-drift-region p⁺-n-n⁺structure.     

Low avalanche noise characteristics in thin InP p+-i-n+ diodes with electron initiated multiplication

We have performed electron initiated avalanche noise measurements on a range of homojunction InP p⁺-i-n⁺ diodes with “i” region widths, w ranging from 2.40 to 0.24 μm. In contrast to McIntyre's noise model a significant reduction in the excess noise factor is observed with decreasing w at a constant multiplication in spite of α, the electron ionization coefficient being less than β, the hole ionization coefficient. In the w=0.24 μm structure an effective β/α ratio of approximately 0.4 is deduced from the excess noise factor even when electrons initiate multiplication, suggesting that hole initiated multiplication is not always necessary for the lowest avalanche noise in InP-based avalanche photodiodes     

0.1-μm p+-GaAs gate HJFET's fabricated using two-stepdry-etching and selective MOMBE growth techniques

This paper reports the first successful fabrication of high-performance, 0.1-μm p⁺-gate pseudomorphic heterojunction-FET's (HJFET's). By introducing the two-step dry-etching technique which compensates for the poor dry-etching resistance of PMMA, 0.1-μm or less gate-openings with a high aspect-ratio of 3.5 in SiO ₂ film are achieved. In addition, by using the gate electrode filling technique with selective MOMBE p⁺-GaAs growth, 0.1-μm voidless p⁺-GaAs gate electrodes with a high aspect-ratio are achieved for the first time. The fabrication technology leads to a reduction of external gate fringing capacitance (Ce^ext _f) in a T-shaped gate-structure and an improvement in gate turn-on voltage. The fabricated 0.1-μm, T-shaped, p⁺-gate n-Al_0.2Ga_0.8As/In_0.25Ga_0.75 As HJFET exhibits a high gate turn-on voltage (V_f) of about 0.9 V, and a good gm_max of 435 mS/mm. Also, an excellent microwave performance of f_T=121 GHz and f_max =144 GHz is achieved due to the C^ext_f reduction. The technology and device show great promise for future high-speed applications, such as in power devices, MMIC's, and digital IC's     

Low-temperature fabrication of p+-n diodes with300-Å junction depth

Gas immersion laser doping (GILD) was used to fabricate p⁺ -n diodes with 300-Å junction depth. These diodes exhibit ideality factors of 1.01-1.05 over seven decades of current, reverse leakage current densities ⩽10 nA/cm² at -5-V reverse bias, breakdown voltages above 100 V, and electrical activation of the boron impurity to concentrations approaching 1×10²¹ atoms/cm³. This behavior is achieved without the use of a furnace or rapid thermal anneal     

High-frequency oscillations of p++-n+-n-n++avalanche diodes below the transit-time cutoff

According to Read, n⁺⁺-P⁺-i-P⁺⁺diodes should oscillate at special high frequencies determined by carrier transit time in the space-charge layer. Oscillations not affected by transit time were observed with p⁺⁺-n⁺- n-n⁺⁺silicon diodes. The corresponding current-voltage characteristic revealed a negative resistance setting in at a critical current. Theoretical considerations show that one-sided avalanche injection in n⁺⁺-p⁺-p⁺⁺structures may lead to a slight negative resistance for carrier concentrations smaller than the impurity concentration and for certain widths of the depletion layer. This type of negative resistance disappears in n⁺⁺-p⁺-i-P⁺⁺structures, but with increasing injection multiplication is induced in the intrinsic layer. Therefore the carrier space-charge is reduced and a negative resistance appears at a critical current density. The onset of this second injection is an upper current limit of the Read transit-time mode. The frequency range of oscillations due to avalanche space-charge feedback generally will not be separated from the range of transit-time oscillations. Thus, it must be judged carefully which mechanism is responsible for observed high-frequency oscillations. On the other hand, space-charge feedback may give additional stability to the transit-time mode.     

X band n+-p-p+ IMPATT diodes

Silicon IMPATT diodes, utilising holes as the drifting carrier, have been fabricated. An output power of 0.5 W with 12% efficiency at X band was obtained.     

Forward current—Voltage and switching characteristics of p+-n-n+(epitaxial) diodes

The forward-biased current-voltage and forward-to-reverse biased switching characteristics of p⁺-n-n⁺epitaxial diodes are investigated. The manner in which the n-n⁺junction affects the flow of injected minority carriers in the epitaxial region is characterized by a leakage parameter a. Experimentally, for diodes with epitaxial film widths much less than a diffusion length, a "box" profile accurately describes the injected minority carriers in the n region. The current is found to increase with increased epitaxial width at a fixed bias. A general switching expression for epitaxial diodes is presented and the validity of the expression is shown experimentally. The experimental values of a, determined independently from the current-voltage and switching characteristics, are in good agreement and show that the leakage of the high-low junction is dominated by the recombination of minority carriers in the n-n⁺space-charge region.     

High-power microwave amplifier using IMPATT diodes

A single multichip IMPATT diode, operating in the unconditional amplifying mode, has been used as a reflection amplifier in the 6?8 GHz range. C.W. power-output levels of 4.0 W have been achieved with a stable reflection-amplifier circuit, using two multichip diodes in separate cavities coupled to a single circulator through an airstrip hybrid. The gain of the amplifier is 6 dB, with 250 MHz (?1 dB) bandwidth.     

A method for the characterization of p+-n-n+diodes using DC measurements

An experimental technique using only dc terminal measurements with a special set of masks is presented for characterizing device properties of single diffused p⁺-n-n⁺diodes. The vertical and lateral current components are separately obtained. The carrier lifetimes in the epitaxial layer and the p⁺diffusion, and the recombination velocity at the oxide-silicon p⁺interface are experimentally determined. Examples are given and possible sources of errors are discussed.     

Corner currents in rectangular diffused p+-n-n+diodes

The low-level injection dc characteristics of rectangular p⁺-n-n⁺diodes are discussed, and the vertical, lateral, and corner current components are analyzed and measured. It is shown that the corner current can be a significant fraction of the total current and a simple analytic expression is given.     

Electrical properties of Ga-implanted Si p+-n shallowjunctions fabricated by low-temperature rapid thermal annealing

p⁺-n shallow-junction diodes were fabricated using on-axis Ga⁶⁹ implantation into crystalline and preamorphized Si, at energies of 25-75 keV for a dose of 1×10¹⁵/cm ², which is in excess of the dosage (2×10¹⁴/cm²) required to render the implanted layer amorphous. Rapid thermal annealing at 550-600°C for 30 s resulted in the solid-phase epitaxial (SPE) regrowth of the implanted region accompanied by high Ga activation and shallow junction (60-130 nm) formation. Good diode electrical characteristics for the Ga implantation into crystalline Si were obtained; leakage current density of 1-1.5 nA/cm² and ideality factor of 1.01-1.03. Ga implantation into preamorphized Si resulted in a two to three times decrease in sheet resistance, but a leakage current density orders of magnitude higher     

Characteristics of an all-implanted p+-n-n+solar cell

This work presents the main electrooptical parameters of a p⁺-n-n⁺single-crystalline silicon solar cell, whose front p⁺-n junction and the backside n-n⁺contact were fabricated through masked ion implantation of boron (¹¹B+) and phosphorus (³¹p+), respectively. The distinctive feature of the cells consists of the use of the front junction silicon dioxide mask as an AR layer in the finished devices.     

Corner currents in p+-n-n+diodes with n+isolation diffusions

The magnitude of corner currents in rectangular diffused p⁺-n-n⁺diodes with deep n⁺isolation diffusions is discussed. Curves are given to illustrate the importance of this current in diodes and IIL structures.