Characteristics of Doping and Diffusion of Heavily Doped N and P type InP and InGaAs Epitaxial Layers grown by Metal Org
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CHARACTERISTICS OF DOPING AND DIFFUSION OF HEAVILY DOPED N AND P TYPE InP AND InGaAs EPITAXIAL LAYERS GROWN BY METAL ORGANIC CHEMICAL VAPOR DEPOSITION
C.J. Pinzone 1, N. T. Ha 2, N. D. Gerrard 3, R. D. Dupuis 1 and H. S. Luftman 2 1 Microelectronics Research Center-, The University of Texas; Austin, Texas 78712-1084 2 AT&T Bell Laboratories; 600 Mountain Avenue; Murray Hill, N.J. 07974 3 STC Defense Systems; Paignton, Devon TQ4 7BE; United Kingdom
ABSTRACT Electronic and photonic device applications of the InGaAs/InP materials system often require the growth of epitaxial material doped to or near the solubility limnit of the impurity in the host material. These requirements present an extreme challenge for the crystal grower. To produce devices with abrupt dopant profiles, preserve the junction during subsequent growth, and retain a high degree of crystalline perfection, it is necessary to understand the limits of dopant incorporation and the behavior of the impurity in the material. In this study, N-type doping above 1019 cm-" has been achieved in InP and InGaAs using Sn as a dopant. P-type Zn doping at these levels has also been achieved in these materials but p type activation above -3 x 1018 cm -3 in InP has not been seen. All materials were grown by the metalorganic chemical vapor deposition (MOCVD) crystal growth technique. Effective diffusion coefficients have been measured for Zn and Sn in both materials from analysis of secondary ion mass spectra (SIMS) of specially grown and annealed samples.
INTRODUCTION InP and InGaAs electronic and photonic devices such as heterostructure bipolar transistors (HBT's)[1], photodiodes[2], lasers and reflectors [3], are of increasing interest for high-speed applications and the possibility of integrated optical, digital, and analog circuits. For these devices, high performance operation requires a reduction in contact resistance. For example, in the case of HBT's , a reduction in the emitter series resistance of the device is required to lower the emitter capacitance for high speed operation. These requirements are met by maximizing the n-type dopant incorporation in the emitter contact and at the emitter base junction. Furthermore, a wider range of device performance can be exploited by expanding the range of n- and p-type doping. Increasing the dopant incorporation in epitaxially grown device structures can lead to degradation of the device performance caused by displacement of the electrical and/or the metallurgical junction caused by diffusion of the dopant species upon further heating of the material as subsequent layers are grown. This problem is more severe in devices that exploit quantum-confinement effects since often the doped layers in such structures are extremely thin (< 300A). It is therefore necessary to investigate the limits of n- and p-type doping and the dopant behavior in the InGaAs/lnP lattice. We have recently reported results for n-type doping with Sn of InP and InGaAs grown by MOCVD using tetraethyltin (TESn) as the dopant source material [4,5,6]
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