GaN by trichloride VPE

Update

Neavs

VPE

CaN by trichloride

ture in an NH3/N2 ambi-

Research News Published

in Journal

ent;

of

Crystal Growth (69 (1996) 689-696) workers at the Solid State Electronics

Lab at Stanford

quartz

Heon

reactor

VPE.

ratio 700.

This is not the first time that trichloride has authors claim, this is the first time the growth mechanism has been clarified by thermodynamics

calcu-

decompo-

sults showed decomposition

that the of the am-

erties.

However,

mal surface

is covered by GaN crystallites around a few mi-

for opti-

morphology

a

monia never reached equilibrium and no more than

higher growth temperature (970°C) and a longer

were therfavoured

10% of it decomposed. These conditions favoured

growth time are desirable.

under these growth conditions. In thermodynamic

GaN deed

deposition and inthe resulting films

equilibrium,

phase

were

single

wall furnace

by HCl

XRD,

PL and SEM charac-

gas

of GaN

was preferred over GaN deposition. Experimental re-

in the paper

Below 95O”C, the surface

Polaroid of the HVPE system.

The layers were prepared in an open-flow horizontal tube single zone hot

etching

500 and

by SEM photos over the range of temperatures.

and of

sition of ammonia hydrogen reduction GaC13 to GaCl modynamically

illustrated

and

the thermodynamic lation. Thermal

between

Surface morphology of the resulting films is

as the

experiment - the paper gives full exposition of

gas.

temperature

was varied over the range 930-1050°C with a V/III

on sapphire by trichloride

but,

to the

by carrier

Growth

grown single crystal GaN

used

that

cell and the va-

pour transported

Lee and James S. Harris, Jr have successfully

been

showed

The GaC13 was melted and heated to 100°C in a

Univer-

sity, CA, USA -

XPS

the surface had been nitrided by this process.

crystal

and

terization showed them to have good defect-free prop-

matic.

-

see sche-

Degreased

and

etched substrates were heated to growth tempera-

crons in size. These coalesce

do not

and the authors

note that there are holes all the way to the substrate. PL spectra showed only bandedge emission at RT implying that each crystallite was of good crystal quality while

XRD

revealed

that

each has a different in-plane orientation. At higher temperatures,

however,

the is-

lands coalesced and gave a smoother surface but there were still grooves

and mi-

croholes present. Hall measurements showed that the layers are highly with a background

n-type conduc-

tivity of a few 10’” cmm3,with RTelectron mobility 3-50 cm*/Vs range.

in the

The work was conducted with assistance from

movable electnc furnace

the US ARPA organisation under contract MDA 972-

/

NH3

i2

gas distribution

Schematic of the GaN hydnde vapor phase epitaxy (HVPE) system.

18

Ill-Vs Review l Vol.10 No.2 1997 0961-1290/97/$17.00 01997, Elsevier

Science

Ltd

N2 pannel

I

I

94-1-0003. Contact: Heon Lee, Solid State Electronics Laboratory, Stanford, CA 94305, USA. Fax: + 1 415 723 4659. E-mail: [email protected]