Disclosed herein are (1) a light-emitting semiconductor device that uses a
gallium nitride compound semiconductor (Al.sub.x Ga.sub.1-x N) in which
the n-layer of n-type gallium nitride compound semiconductor (Al.sub.x
Ga.sub.1-x N) is of double-layer structure including an n-layer of low
carrier concentration and an n.sup.+ -layer of high carrier concentration,
the former being adjacent to the i-layer of insulating gallium nitride
compound semiconductor (Al.sub.x Ga.sub.1-x N); (2) a light-emitting
semiconductor device of similar structure as above in which the i-layer is
of double-layer structure including an i.sub.L -layer of low impurity
concentration containing p-type impurities in comparatively low
concentration and an i.sub.H -layer of high impurity concentration
containing p-type impurities in comparatively high concentration, the
former being adjacent to the n-layer; (3) a light-emitting semiconductor
device having both of the above-mentioned features and (4) a method of
producing a layer of an n-type gallium nitride compound semiconductor
(Al.sub.x Ga.sub.1-x N) having a controlled conductivity from an
organometallic compound by vapor phase epitaxy, by feeding a
silicon-containing gas and other raw material gases together at a
controlled mixing ratio.
