Characterization of Dislocations in (112)B HgCdTe/CdTe/Si J.D. BENSON, 1,4 L.O. BUBULAC, 1 P.J. SMITH, 1 R.N. JACOBS, 1 J.K. MARKUNAS, 1 M. JAIME-VASQUEZ, 1 L.A. ALMEIDA, 1 A.J. STOLTZ, 1 P.S. WIJEWARNASURIYA, 2 G. BRILL, 2 Y. CHEN, 2 U. LEE, 2 M.F. VILELA, 3 J. PETERSON, 3 S.M. JOHNSON, 3 D.D. LOFGREEN, 3 D. RHIGER, 3 E.A. PATTEN, 3 and P.M. GOETZ 3 1.—U.S. Army RDECOM, CERDEC Night Vision and Electronic Sensors, Fort Belvoir, VA, USA. 2.—U.S. Army Research Laboratory, Adelphi, MD, USA. 3.—Raytheon Vision Systems, Goleta, CA, USA. 4.—e-mail: david.j.benson@us.army.mil The electrical performance of HgCdTe/Si photodiodes is shown not to have a direct relationship with the dislocation density as revealed by defect etching. This has led to an equivalent circuit model to explain the relationship of the dislocation density and the electrical test data. A new (112)B HgCdTe/CdTe/Si and CdTe/Si etch pit density (EPD) etch has been demonstrated. The new etch has been used to look for distinctive features which may be responsible for the poor electrical performance of individual diode pixels. The new etch chemistry also reduces the surface roughness of the etched epilayer and makes EPD determination less problematic. The new (to HgCdTe) technique of electro- static force microscopy has also been used to analyze the electrical properties of dislocations. Key words: HgCdTe/CdTe/Si, molecular beam epitaxy, atomic force microscopy, electrostatic force microscopy, etch pit density INTRODUCTION Large-area growth of HgCdTe for thermal imag- ing is primarily performed using (112) Si substrates. The lattice mismatch between HgCdTe and Si is 19%, resulting in a high dislocation density. Heteroepitaxy of CdTe on (112) Si is critical as a buffer layer for subsequent deposition of HgCdTe. As-grown molecular beam epitaxy (MBE) (112)B CdTe/Si has a larger defect density and more dis- ordered crystallinity than bulk (112)B CdZnTe substrates. 1–11 This results in MBE (112)B HgCdTe/ CdTe/Si having a larger defect density and more disordered crystallinity than MBE (112)B HgCdTe/ CdZnTe. MBE-deposited HgCdTe/Si devices are currently available. However, the yield for complex devices (particularly in the long-wavelength region of 9 lm to 12 lm) is still below desired values. This lower than desired yield has been attributed to: defects resulting from the growth process (including lattice mismatch between HgCdTe/substrate); processing- induced damage (including strain relaxation during high-temperature processing, particularly for detectors fabricated on large-lattice-mismatch HgCdTe/CdTe/ZnTe/Si substrates); and the narrow growth 1 and doping window for high-crystalline- quality MBE HgCdTe. Long-wave infrared (LWIR) HgCdTe with an etch pit density (EPD) >5 9 10 5 cm 2 has reduced diode R 0 A. 1,10,11 The resulting higher dark current limits focal-plane array (FPA) operability. The goal of this effort is to examine the impact and nature of dislocations (as revealed by EPD analysis) in MBE (112)B HgCdTe/CdTe/Si. To accomplish this we characterized the correlation between HgCdTe/CdTe/Si EPD and the electrical properties of photodiodes. An analysis of some of the various types of dislocations observed in MBE (211)B HgCdTe/CdTe/Si is presented. EXPERIMENTAL PROCEDURES MBE (211)B HgCdTe/CdTe epilayers deposited on nominal (112) Si were analyzed. 12 The heteroepitaxy (Received December 29, 2009; accepted April 28, 2010; published online May 29, 2010) Journal of ELECTRONIC MATERIALS, Vol. 39, No. 7, 2010 DOI: 10.1007/s11664-010-1262-9 Ó 2010 U.S. Department of Defense 1080