LED Lighting for the 21st Century

阻碍我们的家庭和办公室接受LED照明的一个主要因素是成本。该提案的剑桥部分侧重于通过在硅衬底上生长LED结构来降低成本，硅衬底比通常使用的蓝宝石衬底深得多。我们的工业合作伙伴PhotonStar LED计划使用超薄倒装芯片LED，这意味着必须去除衬底。剑桥大学面临的一个主要挑战是在生长过程中加入一种新的中间层，以促进基板的去除。最初，剑桥大学将使用蓝宝石衬底来测试我们对中间层的想法。例如，提出了在蓝宝石上生长n-GaN，然后是AlGaN中间层，然后是n-GaN的进一步生长，然后是InGaN/GaN的多量子阱。该计划是使用AlGaN中间层来促进蓝宝石衬底和一些n-GaN的去除。在开发了适合在蓝宝石上生长的中间层之后，我们将转向在硅上生长中间层。可能的候选是AlN或SiN。由于在硅上生长的位错密度较高，我们需要引入其他材料的额外中间层来降低位错密度。然后，我们将向PhotonStar LED提供一种超薄，低成本，发射450nm的GaN LED结构。

A major factor preventing the acceptance of LED lighting in our homes and offices is cost. The Cambridge part of this proposal focuses on reducing the cost by growing LED structures on silicon substrates which are much deeper than the sapphire substrates normally used. Our industrial partner, PhotonStar LED, plans to use ultra-thin flip-chip LEDs, which means that the substrate has to be removed. A major challenge is for Cambridge to incorporate a novel interlayer in the growth process which facilitates the removal of the substrate.Initially Cambridge will use sapphire substrates to test our ideas for interlayers. For example, it is proposed to grow n-GaN on sapphire, followed by an AlGaN interlayer, followed by further growth of n-GaN, and then multi-quantum-wells of InGaN/GaN. The plan is for the AlGaN interlayer to facilitate the removal of the sapphire substrate plus some of the n-GaN.Having developed a suitable interlayer for growth on sapphire we will then move to growth on silicon with an interlayer. Possible candidates are AlN or SiN. Because of the higher dislocation densities in growth on silicon we will need to introduce additional interlayers of other materials to reduce the dislocation density. We will then deliver to PhotonStar LED an ultra-thin, low-cost, GaN LED structure emitting at 450 nm.