Semiconductor structure with superlattices

1 . A semiconductor structure, comprising:

a first conductivity type region comprising a first superlattice;

an i-type active region adjacent to the first conductivity type region, the i-type active region comprising an i-type superlattice; and

a second conductivity type region, wherein the i-type active region is between the first conductivity type region and the second conductivity type region;

wherein:

the first conductivity type region is a p-type region and the second conductivity type region is an n-type region, or the first conductivity type region is an n-type region and the second conductivity type region is a p-type region;

the first superlattice is comprised of a plurality of first unit cells;

the i-type superlattice is comprised of a plurality of i-type unit cells;

each of the plurality of first unit cells comprises a first set of at least two distinct substantially single crystal layers;

each of the plurality of i-type unit cells comprises a second set of at least two distinct substantially single crystal layers; and

an average alloy content of the plurality of the first unit cells, and the i-type unit cells is constant along a growth direction;

wherein the structure is configured such that electrons and holes in the structure recombine to generate a spectrum of light, and a longest wavelength peak of the spectrum of light corresponds to a transition between electron and hole confined energy states within the i-type superlattice.

2 . The semiconductor structure of claim 1 wherein the i-type active region has a thickness of greater than or equal to 1 nm and less than or equal to 100 nm.

3 . The semiconductor structure of claim 1 wherein the i-type superlattice comprises from 25 to 400 i-type unit cells.

4 . The semiconductor structure of claim 1 wherein the semiconductor structure is constructed by epitaxial layer growth along the growth direction.

5 . The semiconductor structure of claim 1 wherein the first and second sets of at least two distinct substantially single crystal layers each have a thickness from 1 monolayer to 20 monolayers.

6 . The semiconductor structure of claim 1 wherein one of the at least two distinct substantially single crystal layers within at least a portion of the first or second sets of at least two distinct substantially single crystal layers comprises 1 to 10 monolayers of atoms along the growth direction and another of the at least two distinct substantially single crystal layers in each of the respective unit cells comprise a total of 1 to 20 monolayers of atoms along the growth direction.

7 . The semiconductor structure of claim 1 wherein the at least two distinct substantially single crystal layers of each of the first or second sets of at least two distinct substantially single crystal layers have a wurtzite crystal symmetry and have a crystal polarity in the growth direction that is either a metal-polar polarity or nitrogen-polar polarity.

8 . The semiconductor structure of claim 1 wherein the crystal polarity is spatially varied along the growth direction, the crystal polarity being alternately flipped between the nitrogen-polar polarity and the metal-polar polarity.

9 . The semiconductor structure of claim 1 wherein a maximum of the longest wavelength peak is in a wavelength range of 150 nm to 280 nm.

10 . The semiconductor structure of claim 1 wherein:

the semiconductor structure emits light having a substantially transverse electric optical polarization with respect to the growth direction; and

the semiconductor structure operates as a vertically emitting cavity device with light spatially generated and confined along a direction substantially perpendicular to the plane of the layers of the unit cells of the superlattices of the semiconductor structure.

11 . The semiconductor structure of claim 10 wherein:

the vertically emitting cavity device has a vertical cavity disposed substantially along the growth direction and formed using metallic reflectors spatially disposed along one or more portions of the semiconductor structure;

the reflectors are made from a high optical reflectance metal;

the vertical cavity is defined by an optical length between the reflectors being less than or equal to a wavelength of the light emitted by the vertically emitting cavity device; and

the wavelength is determined by optical emission energy of one or more of the superlattices comprising the semiconductor structure and optical cavity modes determined by the vertical cavity.

12 . The semiconductor structure of claim 11 wherein the high optical reflectance metal is aluminium (Al).

13 . The semiconductor structure of claim 1 wherein:

a reflector layer is provided to improve out coupling of the light generated within the semiconductor structure; and

the reflector layer is positioned atop the semiconductor structure to substantially retroreflect the light.

14 . The semiconductor structure of claim 1 , further comprising a crystalline substrate on which the semiconductor structure is grown wherein a buffer layer is grown first on the crystalline substrate followed by the semiconductor structure with the buffer layer acting as a strain control mechanism providing an in-plane lattice constant.

15 . The semiconductor structure of claim 14 wherein the buffer layer includes one or more buffer layer superlattices.

16 . The semiconductor structure of claim 1 wherein each of the first and second sets of at least two distinct substantially single crystal layers comprises at least one of:

a binary composition single crystal semiconductor material (A x N y ), where 0<x≤1 and 0<y≤1;

a ternary composition single crystal semiconductor material (A u B 1-u N y ), where 0≤u≤1 and 0<y≤1; and

a quaternary composition single crystal semiconductor material (A p B q C 1-p-q N y ), where 0≤p≤1, 0≤q≤1 and 0<y≤1;

where A, B and C are distinct metal atoms selected from group II and/or group III elements and N are cations selected from at least one of a nitrogen, oxygen, arsenic, phosphorus, antimony, and fluorine.

17 . The semiconductor structure of claim 1 wherein each of the first and second sets of at least two distinct substantially single crystal layers comprises at least one of:

a group III metal nitride material (M x N y );

a group III metal arsenide material (M x As y );

a group III metal phosphide material (M x P y );

a group III metal antimonide material (M x Sb y );

a group II metal oxide material (M x O y ); and

a group II metal fluoride material (M x F y );

where 0<x≤3 and 0<y≤4, and where M is a metal.

18 . The semiconductor structure of claim 1 wherein each of the first and second sets of at least two distinct substantially single crystal layers comprises at least one of:

aluminium nitride (AlN);

aluminium gallium nitride (Al x Ga 1-x N) where 0≤x<1;

aluminium indium nitride (Al x In 1-x N) where 0≤x<1; and

aluminium gallium indium nitride (Al x Ga y In 1-x-y N) where 0≤x<1, 0≤y≤1 and 0<(x+y)<1.

19 . The semiconductor structure of claim 1 wherein one or more layers of one or more of the first and/or second sets of at least two distinct substantially single crystal layers is not intentionally doped with an impurity species.

20 . The semiconductor structure of claim 1 wherein one or more layers of one or more of the first and/or second sets of at least two distinct substantially single crystal layers is intentionally doped with one or more impurity species or formed with one or more impurity species.

21 . The semiconductor structure of claim 20 wherein the first conductivity type region comprises an n-type active region, and wherein the one or more impurity species in the n-type active region are selected from:

silicon (Si);

germanium (Ge);

silicon-germanium (Si x Ge 1-x ), where 0<x<1;

crystalline silicon-nitride (Si x N y ), where 0<x<3 and 0<y<4;

crystalline germanium-nitride (Ge x N y ), where 0<x<3 and 0<y<4;

crystalline silicon-aluminium-gallium-nitride (Si u [Al x Ga 1-y ] z N v ) where u>0, x>0, 0<y<1, z>0 and v>0; or

crystalline germanium-aluminium-gallium-nitride (Ge u [Al x Ga 1-y ] z N v ) where u>0, x>0, 0<y<1, z>0 and v>0.

22 . The semiconductor structure of claim 20 wherein the first conductivity type region comprises a p-type active region, and wherein the one or more impurity species in the p-type active region are selected from:

magnesium (Mg);

zinc (Zn);

magnesium-zinc (Mg x Zn 1-x ), where 0≤x≤1;

crystalline magnesium-nitride (Mg x N y ), where 0<x≤3 and 0<y≤2; or

magnesium-aluminium-gallium-nitride (Mg u [Al x Ga 1-y ] z N v ), where u>0, x>0, 0<y<1, z>0 and v>0.

23 . The semiconductor structure of claim 20 wherein the one or more impurity species in the first conductivity type region are selected from:

hydrogen (H);

oxygen (O);

carbon (C); or

fluorine (F).

24 . The semiconductor structure of claim 20 wherein the one or more impurity species are incorporated post growth via ion-implantation.

25 . The semiconductor structure of claim 1 wherein at least a portion of the first superlattice includes a uniaxial strain or a biaxial strain to enhance an activation energy in the portion of the first superlattice to improve an electron or hole carrier concentration.

26 . The semiconductor structure of claim 1 , wherein the semiconductor structure comprises epitaxially grown semiconductor layers comprised solely of superlattices grown along the growth direction.

27 . The semiconductor structure of claim 1 , wherein the average alloy content of the plurality of the first unit cells, the i-type unit cells, and the second conductivity type region is constant along the growth direction.