Control of Zn Doping for Growth of InP pn Junction by Liquid Phase Epitaxy

Abstract

The method of Zn doping for the liquid phase epitax/al growth of a high quality InP pn junction has been investigated. The evaporation of Zn from the growth melt was found appreciable at the growth temperature as low as 640~ and therefore causing the unwanted Zn diffusion into the substrate from the vapor. The diffusion of Zn from the growth melt was also observed and its effective diffusion coefficient in undoped InP was estimated to be 1.0 _.+ 0.3 X 10 -1~ cm 2 sec -I at. 620~176The characterization of grown layers was carried out over a wide range of the Zn doping density. The distribution coefficient of Zn was determined from Hall measurement to be 0.84 below the Zn fraction in the melt of 10 -2 atomic percent. Above this fraction, it was speculated that a strong carrier compensation limits the NA-ND value below 2-3 • 10 TM cm -3 and also results in the energy decrease and the half=width increase of the photoluminescence. In order to eliminate these disadvantages of Zn doping, an improved growth method was developed by an optimized use of in situ etch. The etching of the substrate by pure In solution was found to be characterized by the apparent diffusion coefficient of P in In, 6 • 10 -4 cm 2 sec -1 at 640~ and the structure grown by this method was found free from the misplacement of pn junction and also exhibiting the currentvoltage characteristics of a nearly abrupt junction.

InGaAsP/InP Heterostructure Doped by Cobalt

“…InGaAsP (λ g =1.3µm, d=50nm) and InGaAsP (λ g =1.1µm, d=100nm) are nominally nondoped posses high leakage current. This effect can be caused by the following factors: -the structure defects, especially dislocation network threading through multiheterostructure (PETROFF), -injected carriers may leak through the heterostructure bariers (WADA et al), or the active region is contaminated by zinc from InP:Zn confinement layer (WADA et al, 1980), On the basis of I-V characteristics measured we suggested a modification of prepared multiheterostructure by doping every second a thin layer of InGaAsP (λ g =1.1µm) inside the active region by cobalt. Semiinsulating properties conferred by cobalt impurity can suppress contamination by active impurities and improve the function of heterobarriers during the injection process.…”

LPE Growth Techniques for Fabricating Abrupt Zinc‐ and Magnesium‐Doped p+‐n InGaAsP / InP Heterojunctions

“…As-grown InGaAsP/InP avalanche photodiodes have also shown the lowest leakage current and excess noise factor (15). Zinc, cadmium, and magnesium have been used as p-type dopants for InGaAsP LPE layers (16)(17)(18)(19)(20)(21), but not without problems. Junction misplacement has commonly been observed for zinc-doped epilayers (18).…”

“…Coleman (18) and Wada et a~. (19) capped their melts to reduce cross contamination and thus minimize one source of "anamolous" zinc diffusion. Wada et at.…”

“…Wada et at. (19) have made the most extensive study of this problem, but they did not show C-V, EBIC, or any other direct measurements of junction abruptness. They considered an ideality factor of n -~ 2 for their diodes to be indicative of an abrupt junction, but this is more likely due to surface recombination (22).…”

Application of the point-defect analysis technique to zinc doping of MOCVD indium phosphide

“…The most widely used p-type dopant for MOCVD InP is zinc [4,5]. Epitaxial layers of Zn-doped InP have also been grown using different deposition techniques, such as liquid phase epitaxy (LPE) [6], and both hydride [7] and chloride [8] chemical vapour deposition (CVD). Zinc-doped bulk crystals of InP have been grown by the liquid encapsulated Czochralski (LEC) method [9].…”