Beimplanted 1.3μm InGaAsP avalanche photodetectorsM. Feng, J. D. Oberstar, T. H. Windhorn, L. W. Cook, G. E. Stillman, and B. G. Streetman Citation: Applied Physics Letters 34, 591 (1979); doi: 10.1063/1.90885 View online: http://dx.doi.org/10.1063/1.90885 View Table of Contents: http://scitation.aip.org/content/aip/journal/apl/34/9?ver=pdfcov Published by the AIP Publishing Articles you may be interested in Ion implantation and dry etching characteristics of InGaAsP (λ=1.3 μm) J. Appl. Phys. 74, 1610 (1993); 10.1063/1.354809 On the hotcarrier effects in 1.3 μm InGaAsP diodes J. Appl. Phys. 73, 7978 (1993); 10.1063/1.353909 Reduction of relative intensity noise in 1.3 μm InGaAsP semiconductor lasers Appl. Phys. Lett. 50, 1400 (1987); 10.1063/1.97833 Photoexcited carrier lifetime and Auger recombination in 1.3μm InGaAsP Appl. Phys. Lett. 42, 259 (1983); 10.1063/1.93907 Influence of hot carriers on the temperature dependence of threshold in 1.3μm InGaAsP lasers Appl. Phys. Lett. 41, 1018 (1982); 10.1063/1.93395

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:

130.102.42.98 On: Mon, 24 Nov 2014 13:56:45

Be-implanted 1.3-J..tm InGaAsP avalanche photodetectors M. Feng, J. D. Oberstar, T. H. Windhorn, L. W. Cook, G. E. Stillman, and B. G. Streetman

Department of Electrical Engineering, Materials Research Laboratory and Coordinated Science Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (Received 26 December 1978; accepted for publication 22 February 1979)

The effect of different annealing temperatures in the 450-800°C range on the photoluminescence of Be-implanted InGaAsP has been studied. The results of these measurements indicate that the annealing temperature should be above 700°C for optimum lattice recovery. Avalanche photodetectors with leakage currents as low as 1 p.,A at 100 V and with gains :::: 100 at 116 V have been fabricated. The quantum efficiency for these devices is about 65% throughout the 1.00-1.30-p.,m wavelength range.

PACS numbers: 85.60.Gz, 85.30.De

Within the past few years, the InGaAsP alloy system has become very attractive for both emitters l

-Io and detec­

tors ll-

17 since this alloy can be grown lattice matched to an InP18-2o substrate while still permitting variation of the band­gap energy over a wide range (0.74-1.31 eV). In particular, InGaAsP devices can be fabricated to take advantage of the minimum dispersion and low loss of high-performance opti­cal fibers 21 .22 occurring near 1.27 f.lm.

Although InGaAsP photodetectors have been reported by several research groups, there have been only a few cases where low-leakage-current devices have been obtained. IJ.17

Ion-implanted beryllium is an effective p-type dopant in GaAs,2J-25 GaAsP,26 and InP,27.28 and, recently, implanted Be has been used to form low-leakage-current InP 28 and InGaAsP 17 devices. A critical step in the fabrication of these devices is the annealing of implantation-induced lattice damage. As is the case for other 111-V compounds, it is nec­essary to protect the surface with a suitable encapsulant or a chemical ambient to prevent evaporation or out-diffusion of host atoms during the anneal. The encapsulant used for the work reported here is the same oxygen-free rf-plasma-depos­ited SiJN, as previously used for GaAs annealing. 29

The InGaAsP quaternary layers were grown lattice matched on an InP buffer layer using the step-cooling growth technique described previously. 16 Implants of Be+ were performed at room temperature with (100)-oriented wafers inclined 7° from the ion beam to minimize channel­ing. Beam energies of 100 keY and typical scanned currents of 0.5 f.lA were employed to implant Be to a fluence of 5 X 101' cm-'. Computer-generated statistics using LSS elec­tronic cross sections give a first-order estimate of 0.35 f.lm for the projected range, with a peak Gaussian concentration of - 1.4 X 1019 cm-J prior to annealing. Following implantation the samples were encapsulated on both sides with approxi­mately 2000 A. of plasma-deposited SiJN, at a substrate tem­perature of 350°C.

For the photoluminescence (PL) study, samples were cleaved from a Be+-implanted 5-f.lm epitaxial layer of InoH~Ga().17Aso4Po.6 grown on (100) InP. The room-tem-

perature band gap of this material corresponds to 1.15 f.lm,16 and the alloy composition was determined by electron mi­croprobe measurements. The samples were then encapsulat­ed and annealed for 30 min at a temperature in the 450-800 °C range. For the PL measurements, samples were held at a temperature of 5 OK in a liquid-helium gas-exchange cryostat. Photoexcitation was provided by a 60-m W 5145-A. line from an Ar-Kr laser, and a !-m scanning spectrometer with a dry-ice-cooled lead sulfide photodetector was used to measure the spectral emission. The spectra have not been corrected for system response.

Figure 1 (a) shows the PL spectrum of a typical unim­planted unannealed sample. A broad spectral band with an

ENERGY (eV)

1068 1106 1147 I 181

>-tii Ibl800'C ~ (Anneoll x 10 f--Z

w > ~ ..J W 0::

w U Z w u (/) w z ~ :::J ..J g o I 0-

Icl750'C 1\ , .-/ ~20

Idl700'C 1\ x

~ ~20

'''~~ 1f!550'C!\ x2

.-/ LOO

Igl450'C x400

1161 1121 1081 1041

WAVELENGTH II-'m)

FIG. 1. Typical photoluminescence spectra of Inll."Ga., "Asll .4PIl6: (a) un­implanted, and (b)-(g) implanted with Be to a fluence of 5 X 10" em" at 100 keY. The implanted samples were an­nealed for ~ h at the temperatures shown with 2000-A Si,N, encapsulation. The temperature for these measurements was 5 'K.

591 Appl. Phys. Lett. 34(9). 1 May 1979 0003-6951/79/090591-03$00.50 © 1979 American Institute of Physics 591

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:

130.102.42.98 On: Mon, 24 Nov 2014 13:56:45

FIG. 2. The forward and reverse /- V characteristics of a Be-implanted

In", ,Ga" "As" h ,P" " photodiode.

average half-width of 144 A is observed with two emission peaks at 1.155 and 1.149 eV. This emission corresponds ap­proximately to the expected band-edge luminescence for this alloy composition. As Fig. 1 (g) shows, the implanted sample annealed at 450°C exhibits no detectable PL. Samples an­nealed at 550 and 650 T exhibit weak emission near - 1.119 eV. In contrast, samples annealed above 700°C have a PL peak at 1.133 eV and the intensity of this band increases with annealing temperature. This peak at 1.133 eV is apparently due to luminescence involving the Be acceptor. The lower­energy peak in the spectra for 550 and 650°C anneals may be due to recombination at radiative defects sites which anneal out at higher temperatures. Further work is required to de­termine if these defects involve Be. As the lattice recovers with annealing above 700 °C, a shoulder on the higher-ener­gy side of the Be acceptor luminescence peak, which under higher resolution peaks at 1.155 eV, grows in intensity. This corresponds to the position of the band-edge luminescence observed in the unimplanted spectra. The 1. 149-eV peak could not be resolved presumably due to the strength of the Be-related band. At 5 oK the separation of the assumed Be acceptor peak from the 1.155-eV band-edge peak is 22 meV.

The PL spectra illustrate the strong dependence on lu­minescence efficiency of annealing. Nonradiative recombi­nation centers in incompletely annealed samples compete with radiative process for electron-hole recombination. It is clear from Fig. 1 that annealing temperatures above 700 °C are required for good lattice reordering. After the 800 °C anneal [Fig. l(b)], the integrated intensity of the PL spec­trum is 14% of the un implanted spectrum.

The same Be' implantation and 710 °C temperature an-

592 Appl. Phys. Lett., Vol. 34, No.9, 1 May 1979

FIG. 3. The reverse /- V characteristics ofa Be-implanted InGaAsP photo­detector with and without illumination by a microscope lamp.

nealing procedures were used for a 5-,um

InonGao27AsO.63Po37 epitaxial layer grown on a (100) InP substrate. Photodiodes were fabricated from this material, resulting in a (p+) InGaAsP-(n-) InGaAsP-(n+) InP struc­ture. A 254-,um-diam active area was defined in the center region of the device for the light absorption, and a I-mil-wide gold-zinc alloy contact ring surrounded this active area for collection of the photocurrent. This device was mesa etched using 1 % Br-methanol followed by a 0.1 % Br-methanol etch to increase the device breakdown voltage and reduce the leakage current. The net carrier concentration of the (n-) InGaAsP active layer of this device was determined by C- V measurements to be (l-1.5)X 10" cm-J

• Punch-through of the 4-,um (n-) InGaAsP layer occurred at -90 V.

The J- V characteristics for this photodiode are shown in Fig. 2. The forward voltage is about 0.6 V at 0.1 rnA and 0.8 Vat lOrnA, and the reverse voltage is 104 V at l,uA and 112 V at 10 ,uA. The leakage current of this device varies from I to 80 nA as the reverse voltages increase from 1 to 80 V. Although these leakage currents are still rather high for ei­ther simply reverse-biased or avalanche photodiodes, they are lower than have been previously reported for this compo­sition ofInO.73GaO.27Aso.6JPO .. 17' The influence of a low-inten­sity microscope lamp on the reverse J- V characteristics of this device is shown in Fig. 3. The photocurrent shown indi-

Inc 7POO 27

ASO.slo 37

77a(106~m)=67%

Tja(l15.um) =68%

~ TJa(127f.im) =65"/0

Z o <l. Vl W 0::

~ ___ 1

070 085 I

'00 115

WAVELENGTH (I'm)

.l \ 30 '45

FIG. 4. The relative spectral response (in A/W) of a Be-implanted In" "Ga., "As" h'P" \7 photodetector.

Feng eta!. 592

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:

130.102.42.98 On: Mon, 24 Nov 2014 13:56:45

cates a low-frequency avalanche gain ~ 100 when the device is biased at 116 V, and similar results have been obtained with low-frequency modulated light. As is generally accept­ed, high low-frequency avalanche gain does not necessarily mean that the gain at microwave frequencies will be high and these devices have not yet been packaged for high-frequency pulse measurements. However, the high low-frequency gain and the absence of microplasmas is an indication that these devices will also perform well at high frequencies.

The relative spectral response of this device is shown in Fig. 4. The long-wavelength cutoff is due to the Ino73G~)27Aso.63Po.37 band-gap threshold. The reason for the short-wavelength cutoff at about 0.95 f..lm is not well understood at the present time since the light is incident through the quaternary material, but it is possibly due to residual implantation damage or thermal damage of the up­per surface layer of the InO.73Gao.27Gao.63P037 during the high-temperature anneal. Similar behavior has been ob­served on short-wavelength Be-implanted InGaAsP photo­diodes annealed with a completely different procedure. IJ

•3o

The quantum efficiency of this device is -65% at 1.27 f..lm, and - 67% at 1.06 f..lm. This fabrication procedure thus re­sults in detectors with a fairly constant (around 65%) quan­tum efficiency throughout a 1.00-1.30-f..lm useful wave­length range, and indicates that Be implantation may be a viable means of fabricating low-leakage-current high-gain avalanche photodiodes utilizing lattice-matched InGaAsP grown on InP substrates.

The authors thank G.A. Antypas and R.L. Bell ofVar­ian Associates and R.L. Henry, E. Swiggard, and H. Lessoff of the Naval Research Laboratory for providing InP sub­strates. Discussions with Professor N. Holonyak, Jr., Dr. S. Modesti, M.J. Helix, E.R. Anderson, G.E. Bulman, R.A. Milano, T.R. Lepkowski, and L.M. Zinkiewicz have been very helpful, and we wish to thank B.L. Payne, E.D. Boose, K.A. Kuehl, B.L. Marshall, J.B. Woodhouse, A.B. Wilson, and R.T. Gladin for technical assistance. This research was supported by the National Science Foundation under Con­tract NSF DMR 77-23999, by ARPA through the Office of Naval Research under Contract NOOO 17 -77 -C-0086 (ARPA order No. 3316), by the Office of Naval Research under Con­tract NOOOI4-77-C-0653, and by the Joint Services Electron-

593 App!. Phys. Lett., Vol. 34, No.9, 1 May 1979

ics Program (U.S. Army, U.S. Navy, and U.S. Air Force) under Contract DAAG-29-78-C-00 16.

'A.P. Bogatov, L.M. Dolginov, P.G. Eliseev, M.G. Mil'vidskii, B.N. Sverdlov, and E.G. Shevchenko, SOY. Phys.-Semicon. 9,1282 (1976).

'J.J. Hsieh, App!. Phys. Lett. 28, 283 (1976). 'P.D. Wright, E.A. Rezek, M.J. Ludowise, and N. Holonyak, Jr., IEEE J. Quantum Electron. QE-13, 637 (1977).

'J.]. Hsieh, J.A. Rossi, and J.P. Donnelly. App!. Phys. Lett. 28, 709 (1976). 'CC Shen, J.J. Hsieh, and T.A:Lind, App!. Phys. Lett. 30, 353 (1977). oK. Oe, S. Ando, and K. Sugiyama. Jpn. J. App!. Phys. 16, 1273 (1977). 'T. Yamamoto, K. Sakai, and S. Akiba, Jpn. J. App!. Phys. 16, 1699 (1977). 'K. Sakai, A. Akiba, and T. Yamamoto, Jpn. J. App!. Phys. 16. 2043 (1977).

"H. Nagai and Y. Noguchi, App!. Phys. Lett. 32, 234 (1978). "'P.D. Wright. E.A. Rezek, N. Holonyak, Jr., and G.E. Stillman, App!.

Phys. Lett. 31, 40 (1977). "H.H. Wieder, A.R. Clawson, and G.E. McWilliams, App!. Phys. Lett. 31,

468 (1977). I2A.R. Clawson, W.Y. Lum, G.E. McWilliams, and H.H. Wieder. App!.

Phys. Lett. 32. 549 (1978). "CE. Hurwitz and U. Hsieh, App!. Phys. Lett. 32,487 (1978). "M.A. Washington, R.E. Nahory, M.A. Pollack, and E.D. Beebe, App!.

Phys. Lett. 33, 854 (1978). "T.P. Pearsall and R.W. Hopson, Jr., J. Electron. Mater. 7,133 (1978). "M. Feng, T. Windhom, M.M. Tashima, and G.E. Stillman, App!. Phys.

Lett. 32, 758 (1978). "H.D. Law. L.R. Tomasetta, and K. Nakano, App!. Phys. Lett. 33, 920

(1978). "G.A. Antypas, and R.L. Moon, J. Electrochem. Soc. 120, 1574 (1973). '"R. Sankaran, R.L. Moon, and G.A. Antypas, J. Cryst. Growth 33,271 (1974).

'''R. Sankaran. G.A. Antypas, R.L. Moon, J.S. Escher, and L.W. James, J. Vac. Sci. Techno!. 13,932 (1976).

"D.W. Payne and W.A. Gambling, Electron. Lett. 11, 176 (1975). "M. Horiguchi and H. Osanai, Electron. Lett. 12,310 (1976). 2·P.K. Chatterjee, W.V. McLevige, K.V. Vaidyanathan, and B.G. Street­

man, App!. Phys. Lett. 28, 509 (1976). "M.J. Helix, K.V. Vaidyanathan, and B.G. Streetman, J. Solid State Chern.

13. 426 (1978). "R.A. Milano, M.1. Helix, T.H. Wind hom, B.G. Streetman, K.V. Vaidyan­

at han. and G.E. Stillman, Proc. o/the Symposium on Gallium Arsenide and Related Compounds, St. Louis, 1978, Inst. of Physics, Conf. Series No. 45 (Institute of Physics and Physical Society, London. to be published).

"P.K. Chatterjee, W. V. McLevige, and B.G. Streetman, J. App!. Phys. 47, 3003 (1976).

"J.P. Donnelly and CE. Hurwitz, App!. Phys. Lett. 31, 418 (1977). "W.J. Devlin, K.T. ip, D.P. Leta, L.F. Eastman. G.H. Morrison, and

James Comas, in Ref. 25. '"M.J. Helix. K.V. Vaidyanathan, B.G. Streetman. H.V. Dietrich, and P.D.

Chatterjee, Thin Solid Films 55, 143 (1978). "H.D. Law, K. Nakano, and L.R. Tomasetta (private communication).

Feng eta!. 593

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:

130.102.42.98 On: Mon, 24 Nov 2014 13:56:45