Quantum heterostructures, related devices and methods for manufacturing the same
There is provided a quantum heterostructure and related devices, as well as methods for manufacturing the same. The quantum heterostructure includes a stack of coextending GeSn buffer layers and each GeSn buffer layer has a different Sn content one from another. The quantum heterostructure also includes a quantum well extending over the stack of coextending GeSn buffer layers, the quantum well comprising a highly tensile-strained layer, the highly tensile-strained layer comprising at least one group IV element and having a strain greater than or equal to 1%. The quantum heterostructure is compatible with silicon-based processing, manufacturing, and technologies. The method includes changing a reactor temperature and varying a molar fraction of an Sn-based precursor to achieve a stack of coextending GeSn buffer layers, each having a different Sn composition, on a substrate provided inside the reactor chamber and forming the quantum well over the stack of coextending GeSn buffer layers.
1 . A quantum heterostructure, comprising:
a substrate comprising a strain-engineered material;
a stack of coextending GeSn buffer layers on the substrate, each GeSn buffer layer having a different Sn content one from another, wherein the Sn content of each GeSn buffer layer is comprised in a range extending from 4.9 at. % to 13.4 at. %; and
a quantum well extending over the stack of coextending GeSn buffer layers, the quantum well comprising a highly tensile-strained layer, the highly tensile-strained layer being sandwiched between a bottom barrier layer and a top barrier layer and comprising at least one group IV element and having a strain greater than or equal to 1%, wherein the highly tensile-strained layer has a thickness equal or below 10 nm.
2 . The quantum heterostructure of claim 1 , wherein the at least one group IV element is germanium.
3 . The quantum heterostructure of claim 1 , wherein the stack of coextending GeSn buffer layers comprises between one and six layers.
4 . The quantum heterostructure of claim 1 , wherein the stack of coextending GeSn buffer layers and the quantum well comprise one of: at least one p-type doped layer, at least one n-type doped layer, at least one p-n junction and at least one p-i-n junction.
5 . The quantum heterostructure of claim 1 , wherein the strain ranges from about 1% to about 2%, preferably from about 1.55% to about 1.75%.
6 . The quantum heterostructure of claim 1 , wherein the strain is equal to or higher than 2%.
7 . The quantum heterostructure of claim 1 , wherein, the substrate is one of an Si-on-insulator (SOI) wafer, bulk GE, a Ge-on-insulator (GOI) wafer, a compound semiconductor wafer, a compound semiconductor layer grown on Si, a compound semiconductor layer grown on Ge, a compound semiconductor layer grown on SOI, and a compound semiconductor layer grown on GOI.
8 . The quantum heterostructure of claim 1 , wherein the composition of the buffer layers varies substantially continuously across the stack of coextending GeSn buffer layers.
9 . A method for preparing a quantum heterostructure, comprising:
conditioning a reactor chamber to reach initial growth conditions;
supplying a Ge-based precursor and a Sn-based precursor in the reactor chamber;
forming a stack of coextending GeSn buffer layers on a substrate comprising a strain-engineered material and provided inside the reactor chamber, comprising:
forming a first GeSn buffer layer by exposing the substrate to the initial growth conditions;
conditioning the reactor chamber to reach subsequent growth conditions, comprising:
changing a reactor temperature; and
varying a molar fraction of at least one of the Sn-based precursor and the Ge-based precursor;
forming one or more subsequent GeSn buffer layers on the first buffer layer by exposing the first GeSn buffer layer to the subsequent growth conditions, each GeSn buffer layer having a different Sn content from one another, wherein the Sn content of each GeSn buffer layer is comprised in a range extending from 4.9 at. % to 13.4 at. %; and
forming a quantum well over the stack of coextending GeSn buffer layers, the quantum well comprising a highly tensile-strained layer, the highly tensile-strained layer comprising at least one group IV element and having a strain greater than or equal to 1%, wherein the highly tensile-strained layer has a thickness equal or below 10 nm.
10 . The method of claim 9 , wherein said growing of the stack of coextending GeSn buffer layers and said growing of the highly tensile-strained quantum well are each carried out with an epitaxial growth method, wherein said epitaxial growth method comprises a low-pressure chemical vapor deposition.
11 . The method of claim 9 , further comprising preparing the substrate, said preparing comprising growing a virtual substrate layer on an original substrate layer, wherein said step of growing the virtual substrate layer is carried out at a temperature ranging from about 460° C. to about 600° C. and further comprises thermally treating the virtual substrate layer at a thermal treatment temperature greater than or equal to 800° C.
12 . The method of claim 9 , wherein each buffer layer is grown at a substantially constant reactor pressure, a substantially constant H 2 flow and a substantially constant molar fraction of the Ge-based precursor.
13 . The method of claim 9 , wherein the Ge-based precursor is G e H 4 and the Sn-based precursor is SnCl 4 .
14 . The method of claim 9 , wherein said changing the reactor temperature comprises reducing the temperature and said varying the molar fraction of said at least one of the Sn-based precursor and the Ge-based precursor comprises reducing the molar fraction of the Sn-based precursor.
15 . The method of claim 9 , wherein said forming of the stack of coextending GeSn buffer layers includes supplying at least two of silicon, germanium, tin and carbon precursors.
16 . A quantum heterostructure, comprising:
a plurality of buffer layers on a substrate comprising a strain-engineered material, each buffer layer being made from an alloy and having a different composition one from another, the alloy comprising at least two group-IV elements wherein the Sn content of each buffer layer is comprised in a range extending from 4.9 at. % to 13.4 at. %;
a bottom barrier layer extending over the plurality of buffer layers;
a tensile-strained semiconductor layer extending over the bottom barrier layer, the tensile-strained semiconductor layer being made from one group-IV element and having a strain greater than or equal to 1%, wherein the highly tensile-strained layer has a thickness equal or below 10 nm; and
a top barrier layer extending over the tensile-strained semiconductor layer.
17 . The quantum heterostructure of claim 16 , wherein the alloy comprises at least two of: silicon, germanium, tin, and carbon.
18 . The quantum heterostructure of claim 16 , wherein the tensile-strained semiconductor layer is made from germanium, silicon, carbon, tin or a combination thereof.
19 . The quantum heterostructure of claim 16 , wherein the composition of the buffer layers varies substantially continuously across the stack.