Open tube diffusion of Zn into AlGaAs and GaAs

Cd metal precipitates on the phosphor surfaces. F r o m these results the following m e c h a n i s m is possible for the darkening of the Sulfide phosphor caused by UV light irradiation. Under the UV light irradiation in a h u m i d atmosphere, ZnS and Znl_~CdxS are oxidized owing to a light catalysis oxidization reaction, resulting in the f o r m a t i o n of sulfates containing crystal water and the precipitate of colloidal metals of Zn and Cd on the p h o s p h o r surface. The formation of the colloidal metal layer on the p h o s p h o r surface is b e l i e v e d to be a main cause of the photodarkening phenomena. The bleaching in a dry a t m o s p h e r e is likely due to a reverse reaction against the Zn metal precipitate, since the precipitated Cd m e t a l tends to r e m a i n u n c h a n g e d even after the degraded ZnxCdl_xS was dried. SummarySurfaces of the Znl_xCd~S:Ag,A1 phosphors before and after photodarkening have been analyzed by Auger electron spectroscopy, x-ray p h o t o e l e c t r o n spectroscopy, and x-ray diffraction. The formation of sulfates and the p r e c i p i t a t i o n of Zn and Cd colloidal metals h a v e b e e n o b s e r v e d on the surfaces of p h o t o d a r k e n e d phosphors. The darkening of these phosphors upon exposure to the UV light in a h u m i d a t m o s p h e r e is ascribed to the precipitation of these metals due to photolytic reaction of phosphors. The bleaching of the p h o t o d a r k e n e d phosphors o b s e r v e d in a d r y a t m o s p h e r e is possibly due to the reversible change in Zn metal concentration.Zn-diffusion in GaAs and A1GaAs is a w e l l -k n o w n t e c h n i q u e used extensively for achieving a highly doped shallow p+-layer to facilitate lower ohmic contact resistance and also for forming p-n j u n c t i o n s in various electronic and opto-electronic device structures (1, 2). The e v a c u a t e d sealed-tube diffusion m e t h o d has been used by other researchers (3, 4) for this purpose; however, it was shown to be c u m b e r s o m e and primarily suited for small-scale e x p e r i m e n t a t i o n . An open-tube diffusion method, on the other hand, is simple and can be used for large-scale device processing. In this method, a high Zn vapor pressure is obtained by dissolving Zn in a melt (5) (such as Sn or Ga) or by coating the samples with a film of ZnO-SiO2 (6). F a v e n n e c et al. (7) used an In/Zn alloy source for diffusing Zn into InP, and needed a gas ambient containing PH3 to suppress surface decomposition. This paper will describe a simple open-tube diffusion t e c h n i q u e of Zn into GaAs and A1GaAs in a N, ambient using a granular solid source of ZnGaAs alloy. The idea of using a ternary alloy was first proposed by Casey and P a n i s h (8). Resulting carrier c o n c e n t r a t i o n profiles for both GaAs and A1GaAs are shown and discussed. Selective area diffusion has been p e r f o r m e d in both of these materials using plasma-enhanced chemical vapor deposited (PECVD) Si3N4 and sputtered Si diffusion mas...

Section: Resultscontrasting

confidence: 45%

mentioning

confidence: 99%

A Simple Open‐Tube Zn‐Diffusion Technique for GaAs and AlGaAs

Choudhury¹,

Oren²,

Rothman³

et al. 1987

“…This increase in the diffusion coefficient with the A1 content of the quaternary could be explained by the same mechanism as proposed for the GaAs-GaA1As system in Ref. (14) and (15). These authors interpret this increase of diffusion "velocity" by the decreased concentration of group III vacancies due to a higher binding energy in compounds containing A1.…”

Section: Resultssupporting

confidence: 62%

Zn‐Diffused p‐n Junction in the Quarternary ( Al0.48In0.52As ) z ( Ga0.47In0.53As ) 1 − z

Hallali¹,

Blanconnier²,

Praseuth³

1988

We report on Zn-diffusion in the A1GaInAs quaternary compounds using a semiclosed box technique. An interstitialsubstitutional mechanism is proposed to explain the electrical and atomic profiles. An increase of the diffusion coefficient with increasing A1 content of the layers is observed. C-V measurements at 1 MHz are consistent with an abrupt junction and a constant doping level in the epitaxial layers. The forward current of the diffused junction is exponentially dependent on the applied voltage over several decades of current with an ideality factor n between 1 and 2. The reverse leakage current results from bulk and surface generation-recombination current and tunneling current, as inferred from measurements at various temperatures.

“…Manuscript submitted Sept. 20,1988; revised manuscript received Jan. 29, 1989. This was Paper 752 SOA presented at the Chicago, IL, Meeting of the Society, Oct. [9][10][11][12][13][14]1988.…”

mentioning

confidence: 99%

“…Excellent morphology, reproducibility, and stability are observed. In hddition, the open-tube technique can be scaled up for use with large samples (19,20).…”

mentioning

confidence: 99%

Low Resistance Ti/Pt/Au Ohmic Contacts to GaAs / Al x Ga1 − x As Heterostructures Using Open‐Tube Zn Diffusion

Bulman¹,

Gwilliam²,

Chambers³

1989

Ti/Pt/Au ohmic contacts to p-type GaAs/AI=Gal_xAs heterostructures have been studied as a function of surface dopant concentrations between 6 • 10 TM cm -3 and 8.5 • 10 TM cm -3. The specific contact resistivities as determined from contact resistance measurements employing the transmission line method (TLM) on as-grown molecular beam epitaxially grown structures were at or above 1 • 10 .8 ~-cm 2. Three different conventional TLM metallization patterns were employed in the measurements as well as circular geometry TLM patterns. Open-tube Zn diffusion was employed to increase the surface dopant concentration to 8.5 • 10 TM cm ~ and produced specific contact resistivities as low as 2.5 • 10 .7 ~-cm 2. These values are found to be unchanged after 8000h and remain unaffected by 400~ 2 rain duration anneals.