Some properties of ion-implanted p−n junctions in silicon

Diodes have been made by implantation of boron or gallium ions in n-type, and phosphorus ions in p-type silicon. The doses range from 5 × 10¹² to 10¹⁵ ions/cm², and the energies from 20 to 70 keV. In all diodes the reverse current shows a sharp recovery step upon annealing at 500–600°C. The reverse current after this annealing is typically of the order of 1 nA/cm² at 1 V reverse bias. To overcome the problem of low breakdown voltages usually found for implanted junctions, methods have been developed to enlarge the effective radius of curvature at the edge of the implanted junction. In a planar process with oxide masking, breakdown voltages of 150 V for 3 Ωcm or 1500 V for 300 Ωcm silicon are obtained. This is done by implanting the ions through a tapered oxide, where the oxide walls make an angle of only 3–5° with the silicon surface. The junction depth in this case is 0.4 μm.Another method uses a mask, placed free in front of the slice. Slice and mask rotate during implantation. In this way, a breakdown voltage of 2700 V is obtained with 300 Ωcm silicon.     

A theoretical and experimental study of recombination in silicon p−n junctions

This paper describes the results of a numerical solution of the one-dimensional transport equations as applied to p?n junctions. Generation-recombination is included in the model, and the method of solution is based on that of De Mari. The modifications of Choo are included to allow the solution of problems involving heavy recombination. Theoretical current-voltage characteristics are presented for both uniform and non-uniform distributions of recombination centres, and a comparison is made with experimental results on carbon implanted, silicon, p?n diodes. The dependence of the $\text{I}\text{V}$ characteristics on activation energy, capture cross sections, and density of recombination centres is described. Good agreement between theory and experiment is obtained, and the results suggest that the $\text{I}\text{V}$ characteristics can be described by the sum of two independant components of current. The first component is the generation-recombination current with an exp (eV/mkT) dependence, and the second is the diffusion current with an exp (eV/kT) dependance.     

Impurity distributions and p−n junctions in semiconductors

We have obtained a closed-form solution of the Poisson-Boltzmann equation for a class of quasi-linearly graded p?n junctions. The solution reveals that asymmetric distributions can produce electrostatic potential barriers on the low impurity density side of the junction. For majority carriers these barriers become potential traps producing a secondary space charge next to the primary dipole at the junctions center. The depth of the potential wells depend on the difference in bulk acceptor and donor densities as well as the impurity density slope at the junctions center. Numerical values are given for silicon and germanium.     

Silicon p−n insulator-metal (p-n-I-M) devices

Silicon p-n-I-M devices with thin insulating layers ($\text{thicknesses}\text{? 30}\text{A}\text{?}$), named MTIS devices, have been developed. The two terminal device shows an S-shaped negative resistance characteristics similar to a Schockley diode (or p-n-p-n diode). Typically the threshold and sustaining voltages are 10 ～ 15 and 1.3 ～ 2 volts, respectively. The former however can be controlled by optical illumination. Turn-on time including delay is less than 2 nsec and turn-off time ? 1 nsec or less. A thyristor-like device with its third terminal connected to the n-layer shows switching operation controllable by this terminal. A monolithic linear array of p-n-I-M diodes with 30 μm spacing operates as a shift register through coupling of adjacent diodes. Life of the two terminal devices recorded at present is over 1.5 × 10⁴ hr. These devices can be applied to low power and high-speed electrical switching and also to optical switching and integrated logic circuits.     

Step recovery of p−i−n diodes

Analytical expressions are derived, which give with a good approximation the duration of the constant reverse current phase for pin diodes, in terms of the base lifetime τ, the base width w, and the ratio J_R/J_F of the reverse to forward current.     

Temperature coefficient of resistance for p- and n-type silicon

The temperature coefficient of resistance for n- and p-type silicon has been calculated between ?50 and 125°C for a wide range of concentrations and levels of compensation. These results provide a useful guide for the design of silicon integrated resistors.     

Carrier temperature effects in a p−n junction

Carrier temperature effects arising in a p?n junction are discussed by solving a chosen set of conservation equations. An analytic solution is found for the current flow assuming small departures of the carrier temperature from equilibrium, and a numerical solution involving large carrier temperature variations is presented. The reverse bias at which avalanche breakdown is predicted for a germanium diode is in agreement with experiment.     

Depletion layer formation,space-charge injection and current-voltage characteristics for the silicon p-n-p (n-p-n) structure

Depletion layer formation and current-voltage characteristics are described for the general semiconductor p-n-p (n-p-n) structure in which the impurity or defect centre is able to communicate with both sets of transport levels. All possibilities for current lie within the region bounded on one side by the essentially vertical Shockley-Prim punch-through characteristic and on the other side by the square-law Mott-Gurney space-charge-limited characteristic. If the impurity levels lie near the mid-gap position a variety of characteristics within this region can be expected. Representative current-voltage characteristics have been computed and are described for a typical silicon structure.     

Hall effect study of p-type high resistivity layers on n-type silicon substrates

Analytical expressions for the longitudinal electric field and Hall voltage in p-type high resistivity Halltrons on silicon substrate with opposite conductivity are derived. The effect of Joule heating on the current and Hall voltage has been studied, taking into account the temperature dependence of carrier mobility. It is shown that for p-diffused high resistivity Halltrons on an n-silicon substrate, the theoretical and experimental results are in close agreement.     

An algorithm for two-dimensional simulation of reverse-biased beveled p−n junctions

A technique is described for deriving the boundary condition at the bevel edge of a reverse-biased p?n junction. This boundary condition is used to build a general two-dimensional computer program for the analysis of beveled p?n junctions.     

Ge-doped InxGa1−xAs p−n junctions

The amphoteric properties of Ge in the In_xGa_1?xAscrystals grown by liquid-phase epitaxy are reported. It was found from the Hall measurements that when x < 0·1, the Ge-doped In_xGa_1?xAs was p-type, and when x > 0.1,it was n-type . At the vicinity of x = 0.1, therefore, the In_xGa_1?xAs p?n junction could be made by one growth process. The electrical and photoelectric characteristics of that junction were investigated. The distribution of Ge concentration at the p?n junction, which was obtained from the C-V characteristics, depended on the doping concentrations of Ge. This dependence can be interpreted by analyzing a modified Longini-Green equation. The spectral responses of both photovoltaic effect and electroluminescence showed that in In_0.1Ga_0.9As, Ge atoms gave rise to a heavy compensation effect, and introduced a conduction band tail of states and two kinds of acceptor levels located ～ 20and～ 100meV above the valence band edge.     

Current-voltage characteristics of GaAs p-i-n and n-i-n diodes

Using the same basic equations as Kazarinov et al.[2], but assuming that the product of the electron drift velocity and of the electron lifetime remains constant, we have derived a new formula for the forward d.c. current—voltage characteristic distinguished by the saturated voltage. We have shown that this formula can describe the measured characteristics of some GaAs p-i-n and n-i-n diodes.     

The specific contact resistance of Pd2Si contacts on n- and p-Si

The specific contact resistance ρ_c of Al and Pd₂Si contacts has been measured on p- and n-Si substrates of uniform resistivity. The variation of ρ_c with substrate resistivity is described by the following equations:

The specific contact resistance of Al contacts was found to be lower than the values of Pd₂Si contacts on p-Si. Pd₂Si contacts on both n- and p-Si, (111) orientation, become non-ohmic in the resistivity range $\text{0.020?0.10 Ω-}\text{cm}$.The data in this study are not sufficient to distinguish a variation in ρ_c with substrate orientation. Specific contact resistance values of Pd₂Si contacts on $\text{0.005 Ω-}\text{cm}\text{(100) n-}\text{Si}$ and $\text{0.010 Ω-}\text{cm}\text{(100) p-}\text{Si}$ were not significantly different from values expected for the (111) substrates.     

Properties of n type Ge-doped epitaxial GaAs layers grown from Au-rich melts

Degenerate n-type GaAs epitaxial layers doped with Ge are grown from a Au-rich melt. The layers are typical of those produced via the alloy-regrowth process used to make contacts with AuGe or AuSb + 2% Ge. Traps are found in the forbidden gap with one trap induced by the AuGe complex identified at 160 meV above the valence band edge.     

Crystal damage and the properties of implanted p-n junctions in silicon

The influence of crystal damage on the properties of implanted p-n junctions has been studied by variation of the amount of initial damage, variation of the recovery process, and variation of the residual damage. This was done by carrying out implantations at - 196, 25 and 700°C with 10¹⁵ B⁺/cm² at an energy of 50 keV, and at 25°C with 10¹⁵ BF₂⁺ at an energy of 250 keV and 10¹⁵ Ga⁺/cm² at an energy of 70 keV. Substrate orientations of both 〈111〉 and 〈100〉 were used, and annealing was done in a temperature range between 400 and 1100°C. Gettered as well as non-gettered slices were used for 〈111〉 oriented substrates. The diode properties were analyzed with the aid of Shockley-Read-Hall recombination statistics. Depending upon crystal history and processing, different traps are found to dominate the reverse current. Traps caused by the gettering of contamination as well as those caused by the damage itself play a role. The number of traps is found to be smaller than 10¹²/cm³ for well annealed diodes, resulting in a reverse current density of 0.2 nA/cm² at 1 V reverse bias.     

Shot noise in back biased p-n silicon diodes

An earlier calculation of the noise due to generation of carriers in the space charge region in a p-n silicon diode by Lauritzen and by Scott and Strutt is corrected for the fact that the field distribution in the space charge region of a p-n junction is linear instead of uniform. If the noise is expressed as S_I(f) = 2eIΓ², we find $\text{Γ}{}^2\text{=}\text{11}\text{15}$ in a p⁺n or n⁺p junction, instead of $\text{Γ}{}^2\text{=}\text{10}\text{15}$ found previously.     

Doping effects on the band structure in n-type silicon at 300 K

Based on two screened donor potential models and taking into account the electron-electron interaction effect in the electron-donor interaction, the band-gap narrowing (BGN) in n-type doped silicon at 300 K is investigated. The BGN effect is expressed in terms of physical BGN (ΔE_g), a change in density of conduction-band states (Γ_n) and the change in effective electron (hole) mass (γ_n (γ_p)). In fact, electrical BGN is found to be given by $\text{ΔE}{}_{\mathrm{<mtext>g,\; elec.</mtext>}}{}^1\text{= ΔE}{}_{\mathrm{<mtext>g</mtext>}}\text{+ Γ}{}_{\mathrm{n}}\text{γ}{}_{\mathrm{n}}\text{+ Γ}{}_{\mathrm{p}}\text{+ ΔE}{}_{\mathrm{<mtext>g</mtext><mtext>,\; fd</mtext>}}\text{? ΔE}{}_{\mathrm{<mtext>g</mtext>}}\text{+ Γ}{}_{\mathrm{n}}$, where ΔE_g,fd represents the Fermi-Dirac statistics effect. Our results of $\text{ΔE}{}_{\mathrm{g}}\text{and}\text{ΔE}{}_{\mathrm{tg}}\text{,}\text{elec.}{}^1$ agree fairly with corresponding observed results, and the large values of $\text{Γ}{}_{\mathrm{n}}\text{? ΔtE}{}_{\mathrm{g}}\text{,}\text{elec.}{}^1\text{? ΔE}{}_{\mathrm{g}}$ obtained at high donor concentration are in good agreement with a qualitative discussion given by Marshak and Van Vliet. Finally, the present results for the effective intrinsic-carrier concentration n_ie are compared with corresponding results observed by Tang.     

Post-breakdown bulk oscillations in gold-doped silicon p+−i−n+ double-injection diodes

Experimental work on post-breakdown bulk oscillations in n-type gold-doped phosphorus-compensated p⁺?i?n⁺ double-injection diodes is presented. An empirical relationship for the frequency of oscillation in this region is derived for the first time and discussed.     

Junction potentials of strongly illuminated n+ - p - p+ solar cells

The low-junction (LHJ) model is applied to an n⁺ - p - p⁺ solar cell having finite dimensions, in order to investigate its performance under intense illumination. Ambipolar transport equations are solved in the three sections of the cell using appropriate boundary conditions. Expressions for junction currents are derived, and the junction potentials under open-circuit conditions are computed by the Newton-Raphson method.The theory presented here includes the effects of high level injection. The generalized current density equations which are derived here for an n⁺ - p - p⁺ device are shown to reduce to the ideal Shockley diode equation with appropriate modifications. The effects of p - p⁺ low-high junction on the open-circuit voltage of the cell are explained. The theoretical results of this paper are consistent with the experimental results of others.     

Quenched-in centers in silicon p+n junctions

Silicon p⁺n junctions heat treated at high temperatures (1200°C) for a long time (2–20 hr) and then quenched to room temperatures or below shows two deep donor levels (E_C?264meV andE_C?542meV) in the n-type side of the junction depletion layer which appear to originate from the same imperfection center. The concentration of these levels ranges from 10¹³ to 10¹⁴ cm^?3. The junction leakage current comes from carrier generation at the deeper level in the depletion region. Phosphorus gettering was found ineffective in reducing the concentration of these quenched-in levels, but they are annealed out by very slow cooling (25°C/hr to 650°C then quench to room temperatures). The thermal emission and capture rates of electrons and holes at these levels are measured as a function of temperature and electric field by the junction high frequency capacitance and d.c. leakage current transient techniques. It is demonstrated that the detailed balance relationship does not hold. The origin of this double donor center is yet to be identified.