Totally light controlled static induction thyristor

346

phvsica 129B ( 1985 ) 340 350 North-t to{land, ,Mnsierd:ml

TOTALLY LIGHT CONTROLLED STATIC INDUCTION THYRISTOR Jun-ichi NISHIZAWA, Takashige TAMAMUSHI

and Ken-ichi NONAKA

Research Institute of Electrical Communication, Tohoku University, Sendai 980, Japan * Semiconductor Research Institute, Kawauchi, Sendai 980, Japan

A Totally Light Controlled Static Induction Thyristor is described in this paper concentrating on the optical direct / indirect triggering and quenching mechanisms. Up to tire present time, using two GaAs infrared LEDs (?, - 880nm, T r - I 2nst, 300V - 1.7A is directly triggered and quenched in a turn-on time of 1.9#s and a turn-off time of 6/.as, 540V - 1A is indirectly triggered and directly quenched in a turn-on time of 545ns and a turn-off time of 7.15#s, and 4 0 0 V - 1A is indirectly switched in a turn-on time of 630ns and a turn-off delay time of 660ns.

l t:l)s for direst triggering ol the SI l'h5 and quenching o~

1. INTRODUCTION Tile device structure and the fabrication results of the

the Static Induction Phototransistor (SIPT) [I,12

Static Induction Thyristor (SI Thy) were reported by J. Nishizawa et al. in 19721.

Tile main operational principle

of the SI Thy is the control of the potential barrier height by the Static-induction-effect

to modulate tile forward

2

OPI:RATIONAL P R I N ( ' I P [ I t:ig. 1 shows tile schematic de, Lee cross section ol the

single-buried-gate Sl

I'hy having a quenching p-channel

current of the p-i-n diode between the anode and cathode.

SIPT.

Recently, S1 Thys have been developed up to the highest

ol the SI lhy is refracted through the bexeled surface

data rate of 2300V - 150A. 2500V - 300A and / or 4000V-

between the gate and cathode ek'ctrodes and can penetlale

400A 2-5.

However, the switching operation of those SI

The incident light directly irradiated on lhe surface'

into the n- layer so as to generate electron-hole pairs in l[Iq'

Thys are the electrical turn-on and turn-off. On the other

depletion layer.

Fig.2 shows the energy potential diagram

hand, the conventional Light Triggered Thyristors (LTTs)

and the equivalent circuit at the cathode side of the SI Th},

have been developed up to the highest rate of 8000V - 1200

in the forward blocking state.

A and / or 6000V - 1500A.

stored at the p+ ga~e region, because this region is the

However, as is well-known,

Photogenerated holes arc

they have a weak point of the lengthly turn-off time of a

energy

few hundred ,us during the commutative electrical-turn-oZ?"

electrons are stored at the n- base near the p+ anode region.

process.

The idea of optical triggering of the SI Thy was

When the gate potential is positi~ity biased L_EV(; b> lhu

proposed in 19756 by aaa analogy with a conventional LTT.

excessive stored holes, the potential barrier height for lhu

Then, as far as we know, there have been no reports an

electrons m the n + cathode region is lowered to Vbi(;. K

potential

minimum for holes.

Photogeneralcd

optically-triggered and optically/electrically-quenched GTO.

- 77~VG, although the stored holes in the p+ gate region

The concept of the optical quenching of the SI Thy, which

have a large barrier height of Vbi(-.K - AV(;. When the gate

was proposed in 19797 , is defined by the following optical-

terminal of the SI Thy is open-circuited, the maximum l ) / (

gate-turn-off operation that, if the light sensitive elements

optical gain (current gain! of the £'lTgat~' structure at the

are connected or integrated to the gate electrode of the SI

cathode side is approximately given h} 8-11. as low as lilt'

Thy, it can be optically quenched by the optical irradiation

incident optical power.

on tile light sensitive elements, because a number of holes stored at the gate electrode of the SI Thy during the turn-on state can be discharged through it.

In 1983, the first

experimental confirmation of the Totally Light Controlled SI Thy was carried out by the authors 8-10, using only two

0378-4363/85/$03.30 © Elsevier Science Publishers B.V. (North-Holland Physics Publishing l)ivision )

GKmax -: InK/P(;)IIDn/'W(;I/ll)p,' LI~)] "~ exp [tq/kT~tVbi(; K

VbiG.KI ]

J-l. Nishizawa et al. / Static induction thyristor

347

where n K is the electron concentration of the cathode

the SI Thy is charged up to the turn-on threshold value of

region PG is the hole concentration of the gate region, D n

Vbith as shown in Fig.4. As a result of the optical switching

is the diffusion constant of electrons, Dp is the diffusion

of the normally-on type SI Thy, the anode voltage VAK of

constant of holes, WG is the effective potential width, Lp is

300V at the anode current o f 1.7A is directly triggered and

the diffusion length of holes, q is the unit charge, k is

quenched by two LED light pulses having a triggering power

Boltzmann's constant,

of PLT = 47.7/~W and a quenching power of PLQ = 181/aW.

T

is the

absolute temperature,

VbiGK is the built-in potential between the gate and cathode, and VbiG. K is the potential barrier height at the intrinsic gate point G*.

The term (Dn/WG)/(Dp/L p)

__ SIPT~

ILT

Cathode

diffusion velocity and the exponential term in eqs.(1 ) has a

LTI . 2 tim m

shows the ratio of the electron injecting velocity to the hole

~/~

K=200 p m *

Gate

~

very large value, so that the current gain of the SI Thy at

/IIIIII/II/IIIIIIIII//

00

the cathode side is m u c h larger than those values of the conventional LTTs. The turn-off current gain 5,8 of the SI Thy is said to be more than 10, so that the optically triggered SI Thy can be quenched by the very low power LED pulse irradiated on the quenching SIPT.

3.

Anode

RESULTS AND DISCUSSION 3.1. Experiments Measurements are made on the sample having four

FIGURE 1 Schematic device structure of the single-burieff-gate SI Thy with a quenching p-channel SIPT.

cathode electrode fingers, one finger area of which is shown in Fig.1. Both triggering and quenching LEDs (~ = 880nm, T r = 12ns) are driven by n-channel SITs which are driven by CMOS ICs.

The experimental circuit diagrams and the

operational waveforms are shown in Fig.3 (a), (b), (c) and (d), respectively.

Since the quenching SIPT(TQ) and the

ECG

~J

G' ,IEcK_~~Storedgate holes

reverse biasing voltage VDq are connected in series in the "~,~.~

gate circuit of the SI Thy, operational points corresponding to a turn-on state (A), a turn-off state (C) and a blocking state (D) are determined by the Fig.4, where the current-

LT

x~ \

"N*N~ ~ Re

--

Dark

.... .lug,noted Stored electrons EC~

voltage characteristics of the p-i-n diode between the gate and cathode of the SI Thy and those of the quenching pchannel SIPT as a load are illustrated schematically. 3.2. Direct triggering and quenching In Fig.5 the turn-on delay time Tdo n is plotted as a

TO

gmVg

function of the triggering pulse energy ELT irradiated on the normally-off type SI Thy for seven different triggering powers of PLT' The experimental circuit is shown in Fig.3 (a).

When the incident power PLT is increased beyond 23

CW, the value of Tdo n decreases below 1 /~s at the triggering energy density of 2.5nJ/cm 2. The value of Tdo n is determined by the time required in which the gate potential of

FIGURE 2 Energy potential diagram of the single-gate SI Thy and an equivalent circuit at the cathode side.

348

.I-1 ,~ishizawu cl al / S l a t i c induct~on lh rrLvh)r

'

(a)LO

~'~

'

'

I

I

I I1[

~

1

I

'

I

I I ~[

/

300V 150mA ~q : ~V,VOq: 20V *,:880r~m

VAK

)_

%5 " ~\

I

=gl0 ~

°vVev (d)

(b)

l VGt :Vst TN

RI-'~'~ ----~

LT ~.J LO 90o/,_7@

SI Thy m'/~-

IV0q r~

I I IAK'

L__

!-~

Tdo.%Tr

TdoffTf Til

Z O Z

LT ~

2

--

LQ

I I

I

I

I

10-I

I

L I

I I I[

~

j . ~ l l

Illl

100

101

ENER,GY DENSITy ON ,S{PThy. ELT!nJlc,m,2,),,, 101 ENERGY ON SIPThy ELT(pJ)

!0 2

io0

FIGURE 3 Experimental circuit diagrams: (a) direct trigger and quench, (b) indirect trigger and direct quench, (c) indirect trigger and quench, and (d) operational wavcforms.

f,'I(;URI 5 Direct triggering and quenching ol the nonnally-olf L~l)C SI Thy, tile turn on dela,~ time l '~crstls the incident unergy (density) on the SI Hly I i , T for seven different incident powers of PUF

3.3. Indirect triggering and dirucl quenching fo speed up tile turn-on swiching and to reduce the UlillilllUm trigger power or the Sl 1t/} to much greater degrceb, wc can adopt auxilimy means, StlC]l a:., all ampli fying gate structure or :in indirectly triggered transistor;

Dark d.~.~'Tr-"'--~-~.~E-!

i ;

lh_',ristor structure as 5howll itl Fig,3 (b). indirect-triggered

and

direct-quenched

l'hc optically

switching

watt-

forms of the normally-oil type SI l'hy arc shown in Fig.~, 1-he anode voltage VAK ol 540V at the anode currcn! IAK of 1A is switched with u indirect {riggering power OfPl, I ....

123t*W and a direct quenching powcI or P[.Q - I. 15mW. Response times arc such thaL ldo n : 320ns, 1 r -

\

ioro oo :Vbith

Tdoff = 1.15/~s, I f = 1 3/xs. and ltl

4.7Hs.

225n~.

In Fig.7, the

turn-on delay time Ido n and the ri>,e time ] r are plotted as a function of the incident optical power PLT mJ the triggering SIPT(TT) for several anode voltages,

t o t each

VAK, the turn-off delay, fall, and tailing times of Tdofl. FIGURE 4 Graphical determination of operational points in the gate circuit of the SI Thy.

Tf, Ttl are tabulated m Fig.7

1"he incident power PLr

irradiated on the quenching p-channel SIPT is 1.0roW. Fhe turn-on delay time Tdo n is nearly inversely proportional to the increase of the incident power PL'I' on the other hand, tile rise time T r is almost independent of tile mcidcnl

J-l. Nishizawa et al. / Static induction thyristor

power PLT and is dependent to a high degree on the value

349

3.4. Indirect triggering and quenching To speed up the turn-off switching and to reduce the

of the anode voltage VAK.

minimum quench power of the SI Thy to greater degrees, we can utilize auxiliary means for the gate terminal of the quenching SIPT as shown in Fig.3(c).

The optically

indirect-triggered and quenched waveforms o f the normallyoff type SI Thy are shown in Fig.8.

The anode voltage

VAK of 400V at the anode current IAK of 1A is switched with an indirect triggering power of PLT = 96pW and an indirect quenching power of PLQ = 606/aW. The turn-on time is 630ns and the turn-off delay time Tdoff is 660ns.

!i¸::(~(@!9~i~ii~ii!~i~!~ ~i~i~~:i~;!~i~(i/ii~iii!i~ii/i ~/:~'Q~!@/i~i~iii~i~i!ii~ili!~i/@!/ FIGURE 6 Experimental waveforms of the anode voltage VAK of 540V, the anode current IAK of 1A, and the indirect triggering and direct quenching LED light pulses (LT, LQ), where V~t., = 8.3V, R~t,q = 1MI2, V~uq = - 26V, VGt = 7.5V, RGt = 10b°kg2, and Vst = 5V.

10 7

.....

,,i

.........

Tobte VAK(V) Tdon Tr "[doff(IJ.S) Tf(~S) Tti(p,5) 100

~ 1o ~

200

• o

• *

300 400 500

A o

• •

095 1.10 1.35 1.50 1.50

0.58 0.80 0.95 1.30 1.40

0.80 2.20 2.80 3.40 5.00

[AK=IA, PLQ=I.0mW, X = 8 8 0 n m

FIGURE 8 Experimental waveforms of the anode voltage VAK of 400V, the anode current IAK of 1A, and the indirect triggering and quenching LED light pulses (LT, LQ), where V G = 5 9 V R G = 100ka V D = - 18V, VGt = 12V, RG q= 100ka', Vot q 7.0 V, V ; q ,~q 11.3V, RGq,= 100ka, and VDq ,= - 7.00.

lad

~10 ( 3.5. Totally fight controlled GTO Fig.9 shows experimental switching waveforms o f the

--~.-'.

.

........

1; 0

.-.-.-2-:~

indirectly-triggered

and

directly-quenched

conventional

GTO using the same operational circuit shown in Fig.3 (b). 1610_1

........

1; 1

'

TRIGGERING POWER DENSITY ON SIPT PLT(mW/cm 2)

t 100

,

,

,

t , , , , t

,

101

,

,

, , , , , n

102

TRIGGERING POWER ON SIPT PLT( ~W}

400V - 10A is indirectly-triggered and directly-quenched in a turn-on time of 3ps and a turn-off time of 6ps.

The

incident LED pulse power PLT on the triggering p-channel SIPT is 123pW and the incident light power PLQ on the

FIGURE 7 Turn on delay time Tdo n and turn on rise time T r versus incident power and power density on triggering SIPT (TT), V~b = 8.5V, R~bq = 1Mg2, VDq = -27V, VGt = 8V, RGt 106~2, and Vst = 5V.

quenching p-channel SIPT is 770pW.

The same GTO,

however, cannot be directly triggered with the same trigger power levels of 12.2mW/cm 2, as the gate potential of the GTO is charged up to the value of only 0.6eV. In addition,

,I-I Ni~'hizawa cl a/. / S t a t i c iJlUl~cl#m llz3'ri.v:(,r

350

•

•

c

we find that, if we fail to turn-off the GTO even <)lice, a

also, as pointed out in the elcctrical switching-,

break is ahnost certain I0.

light

controlled

difficult

to

SI I h }

toiali3

h~is Kilt' ~,tfOllg i'l.'attlre o f bcill7

catlso therlnai brt'akdo'~t,i] :1-, COlllpaled l ) lhc

totally light c o n t r o l k ' d ( ; I ().

400V IOA REFERENCES

LT

I. ,I. Nishizawa, ]. Terasaki and J. Shibata, presented a~ IEDM 1972; presented at ESSDERC 1973; Technical Report of Res. Inst. of Elect. Comm., at -rohoku Unix. RIEC TR-30, 1973: IEEE Trans. oil Electron 1)evicts. Vol. ED-22 (1975) 185

0

J. Nishizawa and Y. Ohtsubo. fech. Digest of III)M {Washington, 1980) p.058.

5 pr, ec/div.

Y. Kajiwara. k. Watakabe. M. Bessho. "l'. Yunmnoto and K. Shirahata, ['ech. l)igesl of IEI)M Q~Vashington. 1077) p.38

FIGURE 9 Experimental switching waveforms of tile inderecilbtriggered a n d d i r e c t l y - q u e n c h e d conventional GTO, where V :v. , q = 4 0' V ' R G = 1MEZ '7 V ,t~q . = - 10V. R G t = 1 0 0 k g 2 , andqv'st = 4 . 5 ~ .

4.

V(;t

=

/0V.

4.

Y. lerasawa, K. M i y a t a , S. M t i r a k a i n i , I . Nagano and M. Okamuru. Tech. [)igesl of IFI)M (Washington, 107c)) p.250. J. Nishizawa. K Muraoka, "~ Talnamushi. in piinl in I f l , I l)eviccs.

Kawanlura and I Tfalls. Olt I(Icctroi~

J. Nishilawa, K ,"~akaillt.lia< and I I ()ka. Patcl'I[ Application. No. 5 1 : ) 5 5 8 5

CONCLUSION

lapane~c

file light trigger sensitivity of the SI Thy is inuch highel than that of the conventional L-ITs and the GTO. because

.1. Nishizawa. Japanese 3(~079.

Patenl

Application. No

51

the optical gain of the SIT gate structure is much larger than that

of

the bipolar base structure 9,11

Tile tun>on

threshold voltage of the SI Thy even for tile normally-off type device is smaller than the value of the conventional LTTs. The value of the dv/dt capability of the SI Th3 will be higher than that of the conventional LTI's. because tt/e

S;. .I. Nishizawa, K. Nonaka and I', lamamushi. Stali~ Induction Thyristor, Semiconductor lechnologies 1084, .IARECT, Vol.13, edited b5 J Nishizawa, (OttM & North-Holland ).

F. Tamamushi, K. Nonaka and J, Nishizawa, National Convention Record of II~E Japan, S. 7-2-3. (30th March. 1984).

reverse gate to cathode voltage at tile blocking state can absorb the displacement current component into the gale circuit.

Therefore, S1 Thy ib promissing even as a lighi

triggered thyristor.

In comparison to the conventional

L T T s and the GTO, the SI Thy has many excellent lZ'ature~ such as high speed optical triggering and quenching with the low power LED light, the perfect isolation between high power and control circuits, mininiizing tile number of components and finally low-loss in the total system. And

IO. J. Nishizawa. 1. lamamushi and K, Nonaka, Prec. ~>1 Ihc 1984 Int. Conf. on Solid-State Devices and Materials. (Kobe. Japan, 30th A u g . - 1st Sept. 1~)84) p.321. I1. J. Nishizawa, I. lamanlushi and K. Nonaka. m lU'mI it~ Jotlrnal of Applied Physics. 12. J. Nishizawa, F. lamamushi and S Stlzuki. SII Image Convertor, Semiconductor fcchnologies 1083, JARECT, Vol.8, edited h~ J. Nishizawa !(HIM & North-Holland ).