CN101382964B - GaAs PIN diode equivalent circuit - Google Patents

Abstract

The invention relates to the technical field of monolithic microwave integrated circuits, and discloses a GaAs PIN diode equivalent circuit which is formed by connecting a P+N- junction equivalent circuit unit, an intrinsic-region equivalent circuit unit and an N-N+ junction equivalent circuit unit in series. The method realizes the separate description of the characteristics of the P+N- junctionand the N-N+ junction and the characteristics of the intrinsic region. As the novel GaAs PIN diode equivalent circuit separately describes the junction characteristics and the characteristics of the intrinsic region, veracity can be further improved on the base of the existing GaAs PIN diode equivalent circuit model. Meanwhile, compared with a physical model, the equivalent circuit model has fewerparameters and simple extraction process and the application to circuit design simulation is practical and feasible.

Description

A kind of GaAs PIN diode equivalent electrical circuit

Technical field

The present invention relates to monolithic integrated microwave circuit (MMIC) technical field, relate in particular to a kind of gallium arsenide PIN (GaAs PIN) diode equivalent circuit.

Background technology

Along with monolithic integrated microwave circuit (MMIC) development of technology, the MMIC circuit is widely used in the microwave control circuit, as duplexer, and phase shifter and attenuator etc.The GaAs PIN diode has the cutoff frequency height than High Electron Mobility Transistor (HEMT), and power handling capability is strong, and forward conduction resistance is little, oppositely turn-offs advantages such as electric capacity is little, thereby is widely used in the MMIC control circuit.For the MMIC circuit design based on the GaAs PIN diode, model plays a crucial role.

The model of GaAs PIN diode mainly contains two kinds, and a kind of is physical model, and another kind is an equivalent-circuit model.Wherein, physical model is based on and finds the solution the semiconductor diffusion equation quantitatively, adopts methods such as finite element.Like this, can be on two dimension even three-dimensional analog device characteristic accurately.But the parameter of this physical model is many, and computing time is long, considers from the angle of reality, can only be used for the design and the optimization of individual devices, is infeasible to the simulation of circuit.

For equivalent-circuit model, up to the present, the more equivalent-circuit model of report is to characterize GaAs PIN diode characteristic with intrinsic resistance in parallel and intrinsic capacity in the document, and not to the P+N-knot, the characteristic of N-N+ knot and the characteristic of intrinsic region are described respectively.And in fact, junction characteristic is different with the relation of working direct current with the intrinsic region characteristic, both is distinguished to describe be necessary.

Summary of the invention

(1) technical matters that will solve

In view of this, fundamental purpose of the present invention is to provide a kind of GaAs PIN diode equivalent electrical circuit, and to realize the knot to P+N-, the characteristic of N-N+ knot and the characteristic of intrinsic region are described respectively.

(2) technical scheme

For achieving the above object, the invention provides a kind of GaAs PIN diode equivalent electrical circuit, this circuit is followed in series to form by P+N-knot equivalent electrical circuit unit, equivalent electrical circuit unit, intrinsic region and N-N+ knot equivalent electrical circuit unit.

In the such scheme, described P+N-knot equivalent electrical circuit unit is by the junction resistance R of P+N-knot ₁Junction capacity C with the P+N-knot ₁Be formed in parallel.

In the such scheme, equivalent electrical circuit unit, described intrinsic region comprises an intrinsic region equivalent resistance R _I

In the such scheme, described N-N+ knot equivalent electrical circuit unit is by the junction resistance R of N-N+ knot ₂Junction capacity C with the N-N+ knot ₂Be formed in parallel.

In the such scheme, a stray inductance L further connects in the opposite end that is connected in equivalent electrical circuit unit, intrinsic region in described P+N-knot equivalent electrical circuit unit _S, this stray inductance L _SThe metal lead wire that is and negative pole anodal by the GaAs PIN diode is introduced; A dead resistance R further connects in the opposite end that is connected in equivalent electrical circuit unit, intrinsic region in described N-N+ knot equivalent electrical circuit unit _C, this dead resistance R _CBe between the semiconductor of the electrode metal of GaAs PIN diode positive pole and negative pole and GaAs PIN diode, to produce.

(3) beneficial effect

From technique scheme as can be seen, the present invention has following beneficial effect:

This GaAs PIN diode equivalent electrical circuit provided by the invention, by the equivalence of GaAs PIN diode is P+N-knot equivalent electrical circuit unit, equivalent electrical circuit unit, intrinsic region and N-N+ knot equivalent electrical circuit unit three parts, and P+N-is tied equivalent electrical circuit unit, equivalent electrical circuit unit, intrinsic region and N-N+ knot equivalent electrical circuit unit connect successively, constituted a kind of novel GaAs PIN diode equivalent electrical circuit, realized the knot to P+N-, the characteristic of N-N+ knot and the characteristic of intrinsic region are described respectively.Because this novel GaAs PIN diode equivalent electrical circuit is described respectively junction characteristic and intrinsic region characteristic, so, can on the basis of existing GaAs PIN diode equivalent-circuit model, further improve accuracy.Simultaneously, than physical model, this equivalent circuit model parameter is few and leaching process is simple, and being applied to circuit design simulation is that reality is feasible.

Description of drawings

Fig. 1 is the synoptic diagram of the low frequency equivalent-circuit model of GaAs PIN diode;

Im{ABCD when Fig. 2 is forward bias (1,2) } with the graph of relation of frequency;

Fig. 3 is the sectional view of GaAs PIN diode;

Fig. 4 is the synoptic diagram of GaAs PIN diode equivalent electrical circuit provided by the invention;

To be 10mA and reverse biased at forward current be-correlation curve figure that two kinds of working points of 10V are carried out emulation and test respectively to Fig. 5 for provided by the invention.

Embodiment

For making the purpose, technical solutions and advantages of the present invention clearer, below in conjunction with specific embodiment, and with reference to accompanying drawing, the present invention is described in more detail.

The invention provides a kind of novel ac equivalent circuit model.From the physics working mechanism of device, the GaAs PIN diode is divided into the P+N-knot, intrinsic region and N-N+ tie three parts, to the modeling respectively of every part, are unified into organic whole.

1, P+N-knot

The sign of P+N-knot adopts classical PN junction equivalent-circuit model.At first, calculate the built-in barrier voltage that P+N-ties by (1) formula, calculate the bias voltage of the P+N-knot under certain working direct current again by (2) formula, wherein, J represents current density, J ₀₁The saturation current density of expression P+N-knot.The calculating of space charge region electric capacity and diffusion capacitance utilizes (3) formula and (4) formula respectively.The total capacitance of P+N-knot be space charge region electric capacity and diffusion capacitance and.

${\mathrm{<figure-callout\; id="1"\; label="V\; BJ"\; filenames="H2007101215015E00031.png"\; state="\{\{state\}\}">V</figure-callout>}}_{\mathrm{BJ}}=\frac{\mathrm{kT}}{q}\ln \left(\frac{N_A{N}_D}{{n_t}^2}\right)---\left(1\right)$

$V_{A1}=\frac{\mathrm{kT}}{q}\ln \left(\frac{J}{J_{01}}\right)---\left(2\right)$

${\mathrm{<figure-callout\; id="1"\; label="C\; T"\; filenames="H2007101215015E00031.png"\; state="\{\{state\}\}">C</figure-callout>}}_T=A\sqrt{\frac{\mathrm{\&epsiv;q}{N}_B}{2(V_{\mathrm{BJ}}-V_{A1})}}---\left(3\right)$

${\mathrm{<figure-callout\; id="1"\; label="C\; D"\; filenames="H2007101215015E00031.png"\; state="\{\{state\}\}">C</figure-callout>}}_D=\mathrm{qA}\frac{q}{\mathrm{kT}}{L}_{\mathrm{<figure-callout\; id="0"\; label="P\; p\; n"\; filenames="H2007101215015E00012.png,H2007101215015E00031.png"\; state="\{\{state\}\}">P</figure-callout>}}{p}_n{0}_{}\exp \left(\frac{q{V}_{A1}}{\mathrm{kT}}\right)---\left(4\right)$

C _total1＝C _T1+C _D1(5)

Can reach a conclusion thus: when each layer concentration fixed of GaAs PIN diode is constant, knot

Electric capacity is the function of area and current density:

C _D∞ (A, J).Can from (6) formula

To obtain the intrinsic resistance of P+N-knot.

${\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="H2007101215015E00031.png"\; state="\{\{state\}\}">R</figure-callout>}}_1=\frac{\mathrm{kT}}{\mathrm{qAJ}}---\left(6\right)$

2, N-N+ knot

The N-N+ knot is the height knot, and is all different with PN junction in the calculating of barrier voltage, saturation current density, the few sub-dissufion current of forward.The built-in barrier voltage of N-N+ knot is seen (7) formula.The barrier voltage of height knot is compared much smaller with common PN junction, because Fermi level is all near conduction band.The hole concentration of N-layer can be ignored than the electron concentration of N+ layer, so only consider electron diffusion electric current in the N+ layer, (8) formula of utilization obtains the few sub-dissufion current of forward.

$V_{\mathrm{BJ}2}=\frac{\mathrm{kT}}{q}\ln \left(\frac{n_{\mathrm{on}1}}{n_{\mathrm{on}2}}\right)---\left(7\right)$

$J_{\mathrm{DF}}=J_{\mathrm{Dn}}=\frac{{\mathrm{qD}}_n{n}_{\mathrm{op}}}{L_n}(e^{\frac{q{V}_A}{\mathrm{kT}}}-1)\&ap;\frac{{\mathrm{qD}}_n{n}_{\mathrm{op}}}{L_n}{e}^{\frac{{\mathrm{qV}}_A}{\mathrm{kT}}}---\left(8\right)$

Saturation current density is: $J_0=\frac{{\mathrm{qD}}_n{n}_{\mathrm{op}}}{L_n}---\left(9\right)$

The junction capacity of N-N+ knot and the computation process of intrinsic resistance are identical with the P+N-knot, referring to (3)～(6) formula.

3, intrinsic region

The intrinsic region resistance R _IModulated by conduct charges.GaAs PIN tube voltage is by junction voltage V _jWith intrinsic region voltage V _mForm.Wherein, the relation of Vm and electric current is as follows:

$V_m=I\&CenterDot;R_I=\frac{I}{{\mathrm{qAN}}_D}\frac{w}{u_n+p_{\mathrm{ave}}(u_n+u_p)/N_D}---\left(10\right)$

Wherein, p _AveBe intrinsic region mean void concentration, it characterizes intrinsic region resistance and is subjected to the conduction modulation, is variable resistor.When parameter extraction, can obtain the intrinsic region resistance value by testing apparatus.At first, the S Parameters Transformation that small-signal need be measured becomes the ABCD parameter; Wherein, S is the scattering parameters matrix, and ABCD is the cascade parameter matrix, and the network parameter matrix is to describe network from different perspectives, is applicable to different network conditions, can change mutually therebetween; The S parameter expression be voltage wave, it makes us can be with input, the output relation of the mode define grid of incident voltage ripple and reflected voltage ripple; The ABCD parameter just is particularly suitable for describing cascade network.And the real part matrix Re{ABCD (1,2) of ABCD parameter the value of low frequency can be approximated to be all resistance and.Because the small-signal equivalent circuit of low frequency (near direct current) is approximately shown in Figure 1, Fig. 1 is the synoptic diagram of the low frequency equivalent-circuit model of GaAs PIN diode.

Because contact resistance RC, P+N-knot intrinsic resistance R ₁, N-N+ knot intrinsic resistance R ₂All can ask, be Re{ABCD (1,2) in known all-in resistance } situation under, just can obtain N-district resistance: R _I=Re{ABCD (1,2) }-R _C-R1-R2.

Dead resistance mainly comes from contact resistance, and the value of contact resistance does not change with frequency.The inner lead of PIN diode has been introduced lead-in inductance.Since under high frequency capacitive reactance relatively and induction reactance can ignore, so by the imaginary-part matrix Im{ABCD (1,2) of ABCD parameter } can obtain the value of stray inductance, that is: L=Im{ABCD (1,2)/ω.The imaginary part of ABCD (1,2) and the relation of frequency as shown in Figure 2, Im{ABCD when Fig. 2 is forward bias (1,2) } with the graph of relation of frequency.

4, the equivalent-circuit model structure of GaAs PIN diode

Fig. 3 is the sectional view of GaAs PIN diode, in Fig. 3, has all produced contact resistance between the electrode metal of positive pole and negative pole and the semiconductor, and metal lead wire anodal and negative pole has all been introduced stray inductance, has only marked dead resistance and inductance at positive pole among the figure.

The equivalent-circuit model structure of the GaAs PIN diode of forming by three parts as shown in Figure 4, Fig. 4 is the synoptic diagram of GaAs PIN diode equivalent electrical circuit provided by the invention.Wherein, R ₁The junction resistance of expression P+N-knot, C ₁The electric capacity of expression P+N-knot, this electric capacity comprises space charge region electric capacity and diffusion capacitance; R ₂The junction resistance of expression N-N+ knot, C ₂The space charge region electric capacity of expression N-N+ knot and the electric capacity of diffusion capacitance parallel connection.R _IThe resistance of expression intrinsic layer, it changes with the carrier concentration of injecting, and the carrier concentration of injecting intrinsic layer is subjected to the control of DC current.Represent the stray inductance that causes by microstrip line, R with Ls _CThe ohmic contact resistance that the expression electrode is introduced.

With reference to Fig. 4, this GaAs PIN diode equivalent electrical circuit provided by the invention is followed in series to form by P+N-knot equivalent electrical circuit unit, equivalent electrical circuit unit, intrinsic region and N-N+ knot equivalent electrical circuit unit.

Described P+N-knot equivalent electrical circuit unit is by the junction resistance R of P+N-knot ₁Junction capacity C with the P+N-knot ₁Be formed in parallel.Equivalent electrical circuit unit, described intrinsic region comprises an intrinsic region equivalent resistance R _IDescribed N-N+ knot equivalent electrical circuit unit is by the junction resistance R of N-N+ knot ₂Junction capacity C with the N-N+ knot ₂Be formed in parallel.

A stray inductance L further connects in the opposite end that is connected in equivalent electrical circuit unit, intrinsic region in described P+N-knot equivalent electrical circuit unit _S, this stray inductance L _SThe metal lead wire that is and negative pole anodal by the GaAs PIN diode is introduced; A dead resistance R further connects in the opposite end that is connected in equivalent electrical circuit unit, intrinsic region in described N-N+ knot equivalent electrical circuit unit _C, this dead resistance R _CBe between the semiconductor of the electrode metal of GaAs PIN diode positive pole and negative pole and GaAs PIN diode, to produce.

The material of GaAs PIN diode provided by the invention adopts the preparation of MBE technology.At first, the N+GaAs layer of grow thick 0.4 μ m on the GaAs substrate, the concentration of N+ layer is 3 * 10 ¹⁸Cm ^-3Then, the i-GaAs layer of growth intrinsic on the N+GaAs layer, thickness is 3 μ m, concentration＜10 ¹⁴Cm ^-3At last, growth P+GaAs, thickness is 1 μ m, the surface concentration of P+ layer is 5 * 10 ¹⁹Cm ^-3, be gradient to 1 * 10 to the i-GaAs layer ¹⁸Cm ^-3For forming good Ohmic contact, the electrode of P+ layer adopts Pt/Ti/Au, and the electrode of N+ layer is Ni/Ge/Au/Ge/Ni/Au.The GaAs PIN diode is a mesa structure, as shown in Figure 3.Designed the GaAs PIN diode of three kinds of different sizes altogether: 1. the p type island region radius is 40 microns, and N type district radius is 60 microns; 2. the p type island region radius is 30 microns, and N type district radius is 50 microns; 3. the p type island region radius is 25 microns, and N type district radius is 45 microns.

The present invention also adopts ADS (the Advanced Design System) emulation tool of Agilent company, and GaAs PIN diode equivalent electrical circuit provided by the invention has been carried out square emulation testing.Network analyzer HP8510C is adopted in test, and its measurement range is from 100MHz to 20.1GHz.To be selected in forward current be 10mA and reverse biased is-10V with the dc point of GaAsPIN diode.Below with regard to two kinds of working points difference verification models.

As shown in Figure 5, to be 10mA and reverse biased at forward current be-correlation curve figure that two kinds of working points of 10V are carried out emulation and test respectively to Fig. 5 for provided by the invention.Wherein, a:Ion=10mA, p type island region radius are 40 μ m, b:Ion=10mA, the p type island region radius is 30 μ m, and c:Ion=10mA, p type island region radius are 25 μ m, d:Voff=-10V, the p type island region radius is 40 μ m, and e:Voff=-10V, p type island region radius are 30 μ m, f:Voff=-10V, p type island region radius are 25 μ m.

Above-described specific embodiment; purpose of the present invention, technical scheme and beneficial effect are further described; institute is understood that; the above only is specific embodiments of the invention; be not limited to the present invention; within the spirit and principles in the present invention all, any modification of being made, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (1)

1. a gallium arsenide GaAs PIN diode equivalent electrical circuit is characterized in that, this circuit is followed in series to form by P+N-knot equivalent electrical circuit unit, equivalent electrical circuit unit, intrinsic region and N-N+ knot equivalent electrical circuit unit; Wherein:

Described P+N-knot equivalent electrical circuit unit is by the junction resistance R of P+N-knot ₁Junction capacity C with the P+N-knot ₁Be formed in parallel;

Equivalent electrical circuit unit, described intrinsic region comprises an intrinsic region equivalent resistance R _I

Described N-N+ knot equivalent electrical circuit unit is by the junction resistance R of N-N+ knot ₂Junction capacity C with the N-N+ knot ₂Be formed in parallel;

A stray inductance L further connects in the opposite end that is connected in equivalent electrical circuit unit, intrinsic region in described P+N-knot equivalent electrical circuit unit _S, this stray inductance L _SThe metal lead wire that is and negative pole anodal by the GaAs PIN diode is introduced;

A dead resistance R further connects in the opposite end that is connected in equivalent electrical circuit unit, intrinsic region in described N-N+ knot equivalent electrical circuit unit _C, this dead resistance R _CBe between the semiconductor of the electrode metal of GaAs PIN diode positive pole and negative pole and GaAs PIN diode, to produce.

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