The characteristics of Zn-doped InP using spin-on dopant as a diffusion source

Abstract

INTRODUCTIONThe doping process of Zn is widely used for fabricating InP-based optoelectronic devices. Methods generally used for Zn doping in InP are in-situ doping during the growth and postgrowth ex-situ doping, such as closed ampoule diffusion and diffusion from evaporated Zn-thin film. In-situ Zn doping by metal-organic chemical vapor deposition shows low doping efficiency due to the high-equilibrium vapor pressure of Zn. 1 Moreover, the hole concentration saturates approximately at 1-2 ϫ 10 18 /cm 3 , presumably due to a similar self-concentration mechanism.The most widely used method of Zn doping after the growth step is closed-ampoule Zn diffusion. This method results in a net-acceptor concentration that is much smaller than the Zn concentration. 2 Activation efficiency is about 0.1-10%. Photoluminescence (PL) measurement is quite practical in the investigation of Zn-doped InP. The interstitial and substitutional impurities can be identified from the PL spectrum. The PL characteristics of Zn-doped InP using the closed-ampoule diffusion method were presented by Montie et al. 3 The interstitial donor concentration, N d , after diffusion was not negligible, and the acceptors were partly compensated by the interstitial donors so that the measured net-acceptor concentration was smaller than the Zn concentration. The PL measurement showed dominant donor-to-acceptor (D-A) peak after Zn diffusion. Band-to-acceptor (B-A) peak appeared only after activation anneal. The PL of Zn-doped InP by diffusion from evaporated Zn-thin film showed a similar spectrum with that of the closed ampoule method. 4 This means that the substitutional acceptor is compensated by interstitial Zn acting as a donor. The net hole concentration did not exceed 5 ϫ 10 18 /cm 3 .A doped spin-on glass was used to dope the III-V compound semiconductors. 5 There have been some reports on the Zn diffusion into InP from the spin-on film. 6 Diffusion depth properties can be controlled using this method with In, As, or P codoped spin-on film. 7 In this paper, we describe the method of Zn doping in InP using a spin-on dopant as a diffusion source. The main advantage of this method is that it is carried out in an open system without requiring special treatment to prevent thermal decomposition of the volatile group V component. The actual diffusion process essentially entails the diffusion of Zn through a SiO 2 layer and then into the InP layer. The function of the SiO 2 layer is to preclude chemical or physical effects that may damage the substrate. Area selective doping is possible with a patterned oxide or nitride layer.The optical characteristics of the Zn-doped InP layer were analyzed using a low-temperature PL method. The doping properties are characterized by the differential Hall measurement and secondary ion mass spectrometry (SIMS).Zn diffusion into InP was carried out ex-situ using a spin-on dopant as a diffusion source. The characteristics of Zn-doped InP are analyzed using low-temperature photoluminescence (PL), differential Hall measurement, ...

Optical properties of Zn-diffused InP layers for the planar-type InGaAs/InP photodetectors

“…When the annealing temperature increased over 540 °C, the interstitial Zn atoms could be activated and the distance D-A peak no longer occurs. On the other hand, the (e/D-A) peak at 1.378 eV was observed for Zn diffused InP samples at 540 °C and 620 °C, which has been reported [30][31][32] , indicating that only a few interstitial Zn atoms are left. However, when the annealing temperature increased over 540 °C, the intensity of the e/D-A peak at nearly 1.378 eV substantially decreased.…”

Photodiodes with High Speed and Enhanced Wide Spectral Range

“…This type of diffusion is not realistic for InP-based material systems because the temperature requirement far exceeds the decomposition temperature even when a Group-V decomposition suppressant is used. A relatively new technique for junction formation, at least within the InP/InGaAs material system, is spin-on diffusion (SOD) [12]- [14], a process that has been available for many years for silicon and is still used in some low-cost silicon processes. These days, though, ion implantation and carrier-gas diffusion dominate most silicon production, and spin-on-glass (SOG) doping for silicon has mostly been relegated to undergraduate electronics laboratories because of its relative simplicity and low cost.…”