Diode DC Non-ideal Characteristics

Transcription

1 Dode DC No-deal Characterstcs - e qv/kt V reverse curret ot saturated (geerato the deleto rego) dode breakdow 2 3 recombato the deleto rego l( ) 5 hgh-level jecto of morty carrers l( ) sloeq/ηkt V η η2 seres resstace 4 Chater 2

2 Chater 2 2

3 Reverse Breakdow by valache Multlcato E C E F E V valache Breakdow drft wthout scatterg mact ozato evet V logv BR V BR N.75 B lmted by Zeer breakdow.5 -. ossble hot holes E F Multlcato effect by mact ozato: oly a small orto of electros wth suffcet ketc eergy (hot carrers) s eeded to start a large curret F crt F Ega λ 2q logn B mea free ath betwee collso ( V V ) D max b ε sε N + N D N N for deal abrut dodes V BR N.5. B / 2 Chater 2 3

4 (x) (x)+ (x) (x) (x) x x th B.C. as (x)/m ex (x)m ( α α ) + α Chater 2 4 d d dx x ( α ) α dx α ex ( α α ) M Smlarly, mact ozato ad Multlcato ex ( α ) α dx α ex ( α α ) M x α ( x) + ( x) dx + α ( x ) P dx' dx dx' dx Emrcally, (actually by Shockley as the base for the lucky electro model) b α ex F Usually, α s much larger tha α due to effectve mass M dx

5 Zeer Breakdow ad Bad-to-Bad Tuelg The multlcato rocess ca the be modeled the V relato by M m V VBR M whe V V BR valache Breakdow E ga λ T λ V V BR BR V BR Zeer (tuelg) Breakdow E C E F E V Zeer tuelg (or bad-to-bad tuelg) V E F he F s really large (both N ad N D have to be large), the valece-bad electros ca tuel through the th barrers drectly. he N ad N D are eve larger, a Esak (tuelg) dode wth a N-shae V curve ca hae. J b b * 3 * 2m q FV 4 2m E ex 3 2 4π h E 3qFh ga 3/ 2 ga Chater 2 5

6 Geerato/Recombato Curret Reverse bas: Electros move from Ev to Ec Forward bas: Electros move from Ec to Ev Chater 2 6

7 Forward Bas: J J + J J F D rec s PN Jucto V Equatos qv q qv ex( ) + ex( ) kt 2τ 2kT J s ex qv kt Reverse Bas: J J + J R D ge 2 qd + q N L b d 2τ Forward Bas s the deal factor t lower bases, s aroachg 2 as recombato domates; whle s close to at hgher bases as dffuso domates Chater 2 7

8 Geerato-Recombato sde the Deleto Rego R G R G e q thermalsrh ( E T x x E )/ kt ( G R) τ thermalsrh ( + ) + τ ( + ) e ( E E dx T 2 )/ kt caot use -Δ /τ sce the majorty ad morty carrers are ot easly searable the deleto rego whch cotas the metallurgcal jucto 2 2 reverse-bas before breakdow: << - + -x x Sloe has to be ostve at the edge of the eutral rego, sce the deal V relato: Chater 2 8 d dx for the etre deleto rego

9 2 sde the Deleto Rego wth V q τ G τ + τ 2τ 2 Ths geerato curret results a reverse-bas curret that ever really saturates sce t s tycally larger tha. he other geerato mechasm exsts (such as hoto-geerato), t devates further from. 2 3 small forward-bas rego: >> + - Chater 2 9 for the etre deleto rego Sloe has to be egatve at the edge of the eutral rego, sce the deal V relato: d -x x dx The recombato curret the quas-eutral rego has caused a -V relatosh of η sce all of V s reflected o the searato betwee E F ad E F. the deleto rego, however, sce the otetal chages, the average effect s η2.

10 Seres Resstace ad Hgh-Level jecto R G q 2τ d e qv Vb V + kt / q / kt Chater 2 2τ τ τ 4 Seres resstace the quas-eutral rego: V jucto V Rs 5 R s o the -tye sde wll be roortoal to: e qv / 2 kt e qv / 2 q hgh-level jecto (esecally for + - or + - tyes of dog): -x x x kt μ s larger tha at the edge of the quaseutral rego due to hgh-level jecto. The majorty carrer has to resod to reduce the et charge.

11 Hgh-Level jecto ad dealty Factor Degradato e ca use the ot of vew that the quas-eutral rego has to rema early charge eutral ad ex(qv /2kT) sce the doat charge s smaller tha at x for hgh jecto codtos. R G e qv / ηkt η 2 Chater 2

12 Mult-dmesoal Jucto Dodes Realstc jucto CMOS techology s mult-dmesoal. To create a good test -D jucto dode, usually a large crcle s ecessary. Not oly that s harder to defe, but d wll vary wth the curvature due to the varyg electrc feld mult-dmeso. Usually oly umercal soluto s ossble to obta accurate soluto of the Shockley s equatos. However, dealty factor for the deal art (E F ad E F searated by the aled bas etrely) wll stll be oe, ad a effectve ca be extracted from the deal art of the -V. l N ND l η Chater 2 2