l (1991 ACTA PHYSICA POLONICA A 5
MERCURY ZINC TELLURIDE 10.6 pm AMBIENT TEMPERATURE PHOTODETECTORS
IO OWSKI IGO td O 5 -9 W r z l nd (Received March 21' 1991)
h r t l nd xp r nt l nv t t n f r r z n t ll r d (M b nt t p r t r l n v l n th ph t d t t r r r p rt d h ł- t t d t t v t f M ph t nd t r ( C ph t d d ph t l - tr n t ( EM nd b r d t t r t 1 p h v b n l - l t d f n t n f t r l p t n d p n nd tr f th d v h h h-t p r t r l n v l n th C nd EM d t t r h v b n f br t d fr C -d p d b l M r t l r n b d f d n h/ nn l t hn h r d p rf r n h b n nfr nt d th th r t l pr d t n h n d v r ll r nt It n l d d th t th h h f r f r t t b l t nd h rdn f M th - t r l p r r n p r n t r r d t ll r d nd th t t ll r pl th l tt r n ppl t n f r h h-t p r t r ph t d t t r h p rf r n f h h-t p r t r M ph t d t t r n b f rth r - pr v d b th f pt l r n nt v t nd pt l r n h d v xh b t d t t v t b v r l rd r f n t d h h r th n th r- l d t t r th bn n nd r p n t nd n h v p rf r- n p r bl t th t f l th r l d t t r ACS n b r 7 + 7 E
1 Intr d t n
G n r l n rd r t h v h h n t v t d t t n t n r t r n r t l t th r l tr l n h p ll p rt nt f r d v p r t n n th f r I r n h p r t n f l n v l n th n rr b nd p nd t r ph t d t t n n b f ll xt nd d t b nt t p r t r pr v d d ppr pr t pt z t n f th d v A b nt t p r t r -1 μ Cd ph t nd t r r p rt d fOr th f r t t b tr nd th r l h r r [1- ] Ext n v xp r n- t l nd th r t l t d n h h-t p r t r ph t nd t n h v l b n
(751 75 J. Piotrowski p rf r d n th U K [7- ] th USA [9-11] nd n Y l v [1 ] t b ph l l t t n th h h-t p r t r ph t d t t n r b- I d t t r th r f r pr v nt f th r p rf r n t f pr r p rt n A - b nt t p r t r 1 μ MC ph t nd t n r t pr nt b n ff r d b v r l n f t r r [11 13] h f nd p rt nt ppl t n n d r t nd h t r d n I d t t n t M r r z n t ll r d (M d t t r l t v t b l t nd h h f r f r t nd d t t r pl Cd n ppl t n f r h h-t p r t r l n - v l n th ph t nd t n [1 -19] r r p rt r nt h v nt n th d n nd t hn l f M h h-t p r t r l n v l n th ph t d t t r
h r t l p rf r n f h h t p r t r ph t d t t r
2.1. Performance related semiconductor parameters of MZT
r l l t n f th p rf r n f ph t nd t n t n r t d - t r n th f ll n nd t r pr p rt th b nd p ntr n n ntr - t n b rpt n ff nt nd A r r b n t n t A rd n t l t l [1 ] th b nd p f M v n b
h ntr n n ntr t n l l t d n th xpr n pr p d b óź - nd l [19]
h l tr n nd l ht h l ff t v n b t bl h d rd n t th K n b nd d l
h r P = 5 x 1 -1 nd ∆ = 1 h h v h l ff t v
h l tr n b l t l l t d
h r s = (9 5 x 1 - /x 7 5 r = (9 5 x 1 - /x h f r l (5 d f t n f th b t l [ ] xpr n f r th b t f t t th xp r nt l d t n th 9 x < 1 r n f p t n h l tr n-t h l b l t r t b t n l t 1 M r r n ll r d 1θ μ A b nt p r t r 753
In n rr b nd p r r -b d nd t n nd t h h t p r t r th A r 1 nd 7 pr r th d n nt r b n t n h n [ 1- ] h ntr n A r 1 r b n t n t
1 r v rl p nt r l f p r d l h f n t n h v l f [ 1 ] = h b n d t f t r xp r nt l d t f r x = 1 ÷ 1 h h h-fr n d l tr n t nt f M ppr x t d εf = 15 - x + 13 x (7 h A r 1 nd 7 r b n t n t r
h r z = p/n h r t f ntr n A r 7 t A r 1 r b n t n t l l t d rd n t [ ]
Ab rpt n ff nt l l t d th n th K n d l t n nt - nt th M — r t n h ft rd n t And r n xpr n [ 3] r 1
h th l l t d b rpt n ff nt f ntr n nd p-t p M f n - t n f p t n nd t p r t r A th f r h p-t p d p n n r b rpt n r lt f r d d b ndf ll n ff t 75 J. Piotrowski
2.2. Phooconducor parameters
h h h-t p r t r ph t nd t r n b t f t r l d r b d b pl d l [ ] n h h h ph n n p t ff t rf r b n - t n nd th nfl n f b r nd r d t n n b n l t d t n d r t p l ph t nd t r th n fl f n rr b nd p nd t r r t- n l r n h p h r t v t f th ph t d t t r
h r l, w, d th l n th dth nd th n f th ph t nd t r λ th v l n th f r d t n nd K th nt ff n h nt ff n
h r r1 nd r r fr nt nd b d r fl t n In th pt f r1 = r = 1
h n l-t n p rf r n r d t t v t f ntr n nd t r ph t d t t n l t d b th n d b t t t l fl t t n n h r rr r n r t n nd r b n t n r t In h h-t p r t r ph t nd t n th r r b ll thr r f n t b n d r d th hn n- t th n r t n-r b n t n G nd th 1/f n
h 1/f n n b n z d b ppr pr t f br t n t hn - l t n th 1/f n th r lt n n v lt
h n r l z d d t t v t
Wh n th n r t n-r b n t n n d n t
A n r1 = nd r = 1
h l t xpr n h v t x f r d = /α [1 ] In th M r r n ll r d 1θ μ A b nt p r t r 755
h r
= ατ(z +1/z /n ( h nt t ατ(z+1/z /n n b d n r l z d d p n -d p nd nt f r f r t f nd t r h h d t r n th lt t p rf r n f h h-t p r t r ph t nd t n t v n v l n th r ntr n n- d t r b n l t α τl/n nd t α τ /n r n ll ntr d d th f r f r t r h th n r l z d f r f r t f ntr n nd p- t z d p-t p M f r 1 μ ph t nd t r f n t n f p t n C p t n r r d f r th b t p rf r n n r th d r n t - p r t r d t th t p r t r - b nd p d p nd n f M h n r th p-t p d p n p r d t th ntr n t r l r lt f n r n th z — I/z b rpt n ff nt nd r b n t n t nd h v t x v l t z≈3 A f rth r n r f d p n r lt n d r f nl d t th r p d d r f th A r 7 r b n t n l f t It h ld b n t d th t th l l t d nd r d v l f r ntr n t r l t 3 K r h h r p r d t th n l l t d b Sp r [9]
r 3 h b p r t r f n l d 1 μ - pt z d ph t n- d t n f n t n f d p n In th l l t n b p r d n t f 1 W/ d th v l h v bl n n pt z d h t d p t n d - n A h th n r l z d d t t v t n r th b t l b h n th r l n pr v l At h h b th d t t v t h v th n r t n-r - b n t n n l t A v r d b p r d p t n r r d t h v 75 tr
th x p rf r n h b d ff lt t r l z n pr t h v r It h ld b n t d th t th pt p t n d p n nd d t t r th n d p nd n th b p r d n t t t v t f b t 1 x 1 z 1 / /W n b h v d n pt z d d v (x = 113 z = 3 d = 5 μ th 1 W/ b p r d p t n h l th n r t n-r b n t n n l t f p rf r n M r r n ll r d 1θ μ A b nt p r t r 757
≈ W C l n / x z1t 1 K n r d t t v t b n rd r f n t d ( 5 ; th h v r p n d b n n r f th r p n t
2.3. Photoelectromagnetic detector parameters h ph t l tr n t ff t h l b n d f r b nt t p r - t r M 1 μ ph t d t t n [ -3 ] h d ff n l n th n th n rr b nd p M ll ( d μ h l th b rpt n f 1 μ r d - t n r l t v l (α ≈1 / In h th r d t n n f r l b rb d th n th d ff n l n th nd l r d ff r n n th rf r - b n t n v l t n r f r d r p n f EM d t t r h v lt r p n v t nd d t t v t h b n l l t d n th n r l z d th r f EM ff t v n b l [ ] n th pt f nd 1 r fl t n ff nt t th fr nt nd r r rf r p t v l A n b n ppl d t th EM d t t r th th r l hn n— t n th nl n - r h th l l t d d t t v t f n t n f t r l p t n f r d t t v t - pt z d d p n th n nd n t f ld h x h v- bl v lt r p n v t nd d t t v t f n l d 1 μ d v r f b t 5 /W (f r 1 d d v nd 3 5 x 1 7 z1 / / W r p t v l nd th d t t v t n r b f t r f 9 t K A 7 nd h th pt p rf r n f th n l d d v h v bl th p-t p t r l ( α = x 1 17 -3 nd th n t f ld f h r p n t f d t t v t - pt z d d v f b t 1 n In h h fr n d n th r p n t b l 1 p n b h v d th xp n f p rf r n 75 J. Piotrowski M r r n ll r d 1 μ A b nt p r t r 759
2.4. Dember detectors
h d ff n ph t v lt ( b r ff t r lt fr d ff n f ph - t n r t d rr r [31-33] nd t n r t b t f r n r t n f th ph t v lt th d tr b t n f ph t n r t d rr r h ld b n n f r nd th d ff n ff nt f l tr n nd h l t b d ff r nt h r d nt - ll r lt fr n n n f r pt l n r t n nd fr d ff r n n rf r b n t n v l t t th fr nt nd b rf f th d v h - b r ff t l tr l f ld r tr n th l tr n th h h r b l t h l h l r l r t d th n b th fl x l h b t p rf r n h v- bl f r th n f th d v f th rd r f th d ff n l n th nd f r l r b n t n v l t t th fr nt nd h h t th b rf f th d v h b r ff t d t t n n b n l z d b lv n th tr n p rt nd nt n t t n [31] r 9 h th l l t d n r l z d d t t v t f 1 μ MC b r d t t n f n t n f p t n nd t p r - t r t t v t h h 3 x 1 z1/ /W nd 1 x 1 9 z1/ /W r pr d t d f r pt z d 1 μ d v t 3 nd K r p t v l r 1 h th d p n d p nd n f th l l t d n r l z d r p n v t d t t v t nd r p n t f r n l d 1 μ MC b r d t t r th d t t v t - pt z d th n h b t p rf r n h v d n p-t p d p d t r l h l l t d d t t v t f -3 K b r d t t r h h r p r d t th t f ph t nd t n p r t d t th nd t n r l 7 J. Piotrowski M r r n ll r d 1θ μ A b nt p r t r 7 1
r t n l v lt r p n v t nd n v lt ll b l th n l v l f th b t pl f r p r pr bl n h v n th p t nt l p rf r n h v r r x pl n l d 1 μ d v th z 5 x 5 μ ll h v r t v t nd n v lt f f 5 p / z 151 / h r r Ω p bl t v r th d ff lt h n nn t n f ll r b r d t t r n r r x pl t bt n r n bl r t v t (~ 5 Ω n 1 t t l r n t v l nt f n l d 1 μ d t t r t n r t d v d t r nt 5 x 5 μ t l nt nn t d n r th l r t v t nt r nn t n S h d v f bl th th d f d rn - r l tr n h r p n t f d t t v t pt z d d v f b t 1 n d - r n th p-t p d p n t xp n n p rf r n h fr n pt z d b r d t t n h ld b pr p r d fr tr n l d p d t r l nd th r th n h ld b pt l r x pl f r d t t n th α = 5 x 1 17 -3 nd d = μ τr ≈5 p An th r p bl l t t n f th r - p n t th RC n t nt n t p rt nt d t th l r t v t nd l p t f b r d t t r
2.5. Phoodiodes
h t d d h v b n xt n v l d pr r l l d h h p d d t t n f CO l r r d t n n th d r t nd h t r d n d nd n th r l n t n 3-5 nd -1 μ t ph r b nd h d v h v l p t nt l f r p r t n t l v t d t p r t r h l l t d p rf r n f ph t d d l htl l r p r d t th t f ph t nd t n b t h h r p r d t th t f EM d t t r h l n r l z d r t v t nd r p n v t r l r tr t th f l- n f nv nt n l ph t d d t th h rt nd d v b nd r x - pl th r t v t f 1 x 1 μ 1 μ ph t d d p r t d t 3 nd K l t b t 5 nd 1 Ω r p t v l Und r h nd t n th n f pl fl r b v th d d n h n bl t h v th p t nt l d t - t v t f th d v nd th th r n h ph t nd t n nd EM d t t r r t pr nt th t fr ntl d ph t d t t n f r h h-t p r t r p- pl t n
3 h t d t t r f br t n nd r d p rf r n
h b nt t p r t r ph t d t t r h v b n f br t d fr b l C -d p d M r t l r n b th n h/ nn l t hn [3 ] r 11 h th t t r f th h h-t p r t r ph t nd t n nd EM d t - t r h d v r th n fl f n rr b nd p nd t r ppl d th l tr d nd f x d t h t nd t v b tr t h pr p r t n f th d - v n l d d p t n f nS nd ld l r n r f ll p l h d f r f n p x n th f r t l n r pph r b tr t p l h n th f r t t f n l th n f b t 5 μ d l n t n f t v r nd t ll z t n f r 7 J. Piotrowski
nt t l tr d h th n f th p x l r h ld b l 1 μ f r d h t d p t n In th f EM d t t r th b rf f th p l- h d n f r bj t d t tr t nt f r h h rf r b n t n v l t h n t v l nt r h d n h h-fr n n h EM l - nt r nt d n h n h h n rp r t n t r p r n nt - n t h f r r rth n t t r l ll t bt n n t f ld b v 1 h b v - v r r d d t t v t f th b nt t p r t r ph t d t t n h n n nd 5 h r d p rf r n f C nd EM d t t r n rd r f n t d h h r p r d t n p r l tr d t - t r th bn n nd r p n t nd ph t n dr d t t r A p r n f th xp r nt l r lt th th th r h th t t t ll p bl t pr v th p rf r n n f ntl
b l t f f rth r pr v nt f th p rf r n
4.1. Optical immersion
h pt l r n f d t t n nt h h r fr t n nd x h ph r l r h p r ph r l l n r d th z b f t r d p nd nt n n th r fr t n ff nt f th l n h z r d d b f t r l t n f th d t t r pl d n th nt r f h ph r l l n r b n f th d t t r pl d t th f r t W r tr p nt f h p rh ph r l l n xt nd n b nd th ntr f th ph r W th pt l r n l r d t t r r pl d b ll r n th t h th v l nt pp r nt pt l r h r n n r th n r l z d d t t v t b f t r l t n n th f h ph r l r n nd b n n th t f h p rh ph r l r n [35-3 ] p t th l r n r f d t t v t h ph r l r n fr - ntl d f r th f ll n r n h h ph r l 1 n b n l d d n th x t n pt l t n n h n n th p t n f th f l pl n M r r n ll r d 1θ μ A b nt p r t r 763
and introducing no restrictions on the system numerical aperture. A hyperspheri- cal lens will introduce an image shift that will increase with the lens radius, and the maximum numerical aperture of the host system is determined by the refrac- tion coefficient. The higher n, the slower the optics. The significant reduction of the electrical area of the immersed detectors compared to the optical one results in a significant reduction (by a factor of n or n 5 ) of the bias power. This is an important advantage in the high temperature photoconductors, which for the best performance, require high biasing. For the best result, the materials for immer- sion lenses should have a high refraction coefficient and low absorption at the wavelengths of interest. Reflection losses can be prevented by the use of a suit- able antireflection coating of the lenses. Germanium (n = 4) is typically used for r n l n h h n p r t b th n th 3-5 μ nd -1 μ b nd - ntl n l th pt ll r d h h-t p r t r ph t d t t n h v b n r p rt d [37] n h h th l n r f r d n b tr t f d t t r p l r Optical immersion seems to be very promising for photodiodes and Dember detectors. Apart from the usual n or n gain, immersion results in a large increase in resistivity. For example, the resistivity increases by a factor of n = 256 with the use of Ge hyperimmersion lens, compared to that of a conventional device of the same apparent area, highly easing matching to low noise preamplifiers.
Resonant optical cavity
The voltage responsivity and detectivity increase with decreasing thickness of a photoconductor if the quantum efficiency remains high. The effective absorption of radiation in thin photoconduction can be increased using the interference effect to set up the resonant optical cavity. The structure of the resonant cavity consists of a semiconductor flake, is sandwiched between two dielectric layers, with the rear dielectric layer surface covered with a highly reflective coating. All the surfaces must be sufficiently flat. It has been shown [38] that the use of an optical resonant cavity can improve the performance of photoresistors by a factor of 2.5 and an improvement by a factor of 5 is possible for photodiodes, Dember and PEM detectors.
4.3. Non-equilibrium devices
Recently, British workers have shown that the performance of high-tempera- ture longwavelength photoresistion and photodiodes can be improved with the use of exclusion and extraction effects at 1-h or at heterojunction contacts [39-41], making possible to achieve BLIP performance at near room temperature. The practical realization of such devices will require well established epitaxial technol- ogy, but the first practical non-equilibrium (Hg,Cd)Te devices/ based on existing technology have already been demonstrated. 7 tr
C n l n 1 h f r f r t r p n v t r p n t nd lt t p rf r n f -3 K l n v l n th M ph t nd t r ph t d d - b r nd EM d t t n h v b n l l t d f n t n f t p r t r p t n d p n nd th r f t r It h b n h n th t th b nt t p r t r 1 μ ph t d t t r h v n bn n nd r p n t n h v p rf r n f th l th r l d t t r h h h t p r t r M ph t nd t n nd EM d t t n h v b n f br t d fr C -d p d b l M r t l r n b th n h/ nn l t hn nd h r t r z d 3 h pt z d " nv nt n l" b nt t p r t r 1 μ M ph t n- d t r nd b r d t t n n h v d t t v t h h r th n 1 z1/ /W h p rf r n f b nt t p r t r ph t d t t n n b pr v d n th pr n pl f pt l r n nt v t nd pt l r n I - r n l f l t t t h n f ph t d d nd b r d t t n t l -n l tr n n bl n t h v th r p t nt l p rf r n S h d v th bn n nd r p n t n rp th p rf r n f th b t l th r l d t t r 5 A f rth r pr v nt f p rf r n p bl b th f n n- - l br ff t t th l-h r t h t r j n t n nt t h b n t n f ll th th d v nt ll ll t h v th I p rf r n t n r b nt t p r t r
f r n [1] tr Properties of HgCdTe Layers, h h M l t r A d f S n W r 197 ( n l h [ ] tr Electron Technol. 5 7 (197 [3] E I r r tr n Proc. 6th Symp. of IMEKO
Technical Committee on Photon Detectors, Siofok - Budapest 1987, IMEKO S r - t r t -1371 d p t 197 p 1 [ ] W G l r tr Infrared Phys. 19 9 (1979 [5] W G l rr Laser Focus, 7 (19 [ ] tr A l ółprz dn d t t r p d z r n W W r z 19 5 ( n l h nd r l t d p p r t d th r n [7] C E tt Handbook on Semiconductors 7 7 (19 1 [ ] A C p A r r M C W l n E l n E Wr n Proc. 2nd Inter. Conf. on Advanced Infrared Detector and Systems, I EE nd n 19 3 p [9] Sp r n Proc. of IRIS Specialty Group on IR Detectors, S n 19 p 1 [1 ] Sp r n Proc. of IRIS Active Systems, S n 19 p 331 M r r n ll r d 1 μ A b nt p r t r 7 5
[11] S W n Lasers and Applications, 59 (19 7 [1 ] j r tr j n v Electron. Lett. 159 (19 [13] IGO td r l d t h t W r ( l nd [1 ] A Sh r A Sh n W E Sp r C K Sh h J. Vac. Sci. Technol. A 3 1 5 (19 5 [15] A Sh r E r A l Appl. Phys. Lett. 59 (19 5 [1 ] K Ad A M tr Appl. Phys. Lett. 5 1 3 (19 9 [17] r M h tr Phys. Status Solidi A 11 K37 (19 9 [1 ] l Gr n r S nd r b l t J. Phys. 7 (19 7 [19] K óź A l Infrared Phys. 1 1 (19 [ ] b E St r S r K l J. Appl. Phys. 53 3 (19 [ 1] E t r n Semiconductors and Semimetals 1 1 1 (19 1 [ ] C l n J. Appl. Phys. 5 (19 1 [ 3] W W And r n Infrared Phys. 3 3 (19 [ ] l Phys. Rev. B 7 (1973 [ 5] W G l M Gr dz n dz l tr n Proc. 9th Symp. of IMEKO Tech. Comm.' Visegrad 1980, IMEKO S r t r t d p t 19 p 3 [ ] dz l Design of MCT PEM Detectors, h h M l t r A d f hn l (WA W r 19 3 [ 7] G nz A óź K óź dz l tr Infrared Phys. 1 (19 [ ] K óź M tr Infrared Phys. 371 (19 [ 9] dz l tr J. Tech. Phys. 7 5 (19 [3 ] M Prog. Quantum Electron. 11, (19 7 [31] A th G nz K rr nn Photoelectrische Erscheinungen, A d rl rl n 1977 [3 ] dz l tr f. Tech. Phys. 173 (19 7 [33] dz l tr J. Tech. Phys. 75 (19 7 [3 ] tr t J. Cryst. Growth 9 37 (19 [35] E Sl v nd l Infrared Phys. 1 1 5 (19 1 [3 ] I C C r h l A n W l n Advances Infrared Detector and Systems, IEE nd n 19 3 p 5 [37] M Gr dz ń tr Infrared Phys. 9 51 (19 9 [3 ] dz l (t b p bl h d [39] A hl C E tt Electron Lett. 1 51 (19 5 [ ] A hl C E tt A r r Infrared Phys. 3 3 (19 [ 1] C E tt n Proc. Symp. on Narrow Band Gap Semiconductors Gaithersburg, Ed G S l r C tt r r t l Y r 199 p S-3