Method for manufacturing micro-LEDs

A method for manufacturing micro-LEDs, the method comprising:

• (a) providing an initial stack comprising a support layer, a non-intentionally doped GaN layer, a strongly n-doped GaN layer, an n-doped GaN layer, the quantum wells, a p-doped GaN layer, and a first electrode;
• (b) transferring the initial stack onto a support substrate covered with a metal layer;
• (c) removing the support layer, and optionally buffer layer comprising (Al,Ga)N, the non-intentionally doped GaN layer, to obtain a substrate of interest comprising the support substrate, the first electrode, the p-doped GaN layer, the GaN/InGaN quantum wells, the n-doped GaN layer and the strongly n-doped GaN layer;
• (ii) forming mesas in the stack;
• and
• (iii) covering the porosified GaN layer with a second electrode formed by a conductive transparent oxide layer, the second electrode being in direct contact with the porosified GaN layer;
• or
• depositing a second electrode over a lateral face of the porosified GaN layer or over a lateral face of the n-doped GaN layer and covering the porosified GaN layer with an encapsulation layer, the encapsulation layer being in direct contact with the porosified GaN layer,
• wherein the porosifying (ii) is optionally carried out before or after the forming (iii),
• wherein the porosifying is (ii) carried out so that a GaNp optical index of the porosified GaN layer, which is neff, does not vary by more than 10% with respect to an E2 optical index of the second electrode and/or with respect to an EL optical index of the encapsulation layer.

A method for manufacturing micro-LEDs, the method comprising:

• providing a stack comprising a support layer, a non-intentionally doped GaN layer, a strongly n-doped GaN layer, an n-doped GaN layer, quantum wells, a p-doped GaN layer, and a first electrode;
• forming mesas in the stack, by etching the first electrode, the p-doped GaN layer, the quantum wells, the n-doped GaN layer, the strongly n-doped GaN layer;
• and a portion of the non-intentionally doped GaN layer;
• porosifying the strongly n-doped GaN layer, to obtain whereby a porosified GaN layer in an obtained stack;
• transferring the obtained stack onto a support substrate covered with a metal layer;
• removing the support layer, the non-intentionally doped GaN layer, to obtain a substrate of interest comprising the support substrate, the first electrode, the p-doped GaN layer, GaN/InGaN quantum wells, the n-doped GaN layer, and the strongly n-doped GaN layer;
• and
• covering the porosified GaN layer with a second electrode formed by a conductive transparent oxide layer, the second electrode being in direct contact with the porosified GaN layer;
• or
• depositing a second electrode over a lateral face of the porosified GaN layer or over a lateral face of the n-doped GaN layer and covering the porosified GaN layer with an encapsulation layer, the encapsulation layer being in direct contact with the porosified GaN layer,
• wherein the porosifying is carried out before or after the forming,
• wherein the porosifying is carried out so that a GaNp optical index of the porosified GaN layer, which is neff, does not vary by more than 10% with respect to an E2 optical index of the second electrode and/or with respect to an EL optical index of the encapsulation layer.

A micro-LED structure, comprising:

• a stack comprising a porosified strongly n-doped GaN layer, an n-doped GaN layer, quantum wells, a p-doped GaN layer, a first electrode, mesas being formed in the stack,
• wherein the porosified GaN layer is covered by and in direct contact with a second electrode, formed by a conductive transparent oxide layer, the second electrode being optionally covered with an encapsulation layer,
• or
• wherein a second electrode is arranged over a lateral face of the porosified GaN layer or over a lateral face of the n-doped GaN layer, the porosified GaN layer being covered by and in direct contact with an encapsulation layer,
• wherein a GaNp optical index of the porosified GaN layer does not vary by more than 10% with respect to an E2 optical index of the second electrode and/or with respect to an EL optical index of the encapsulation layer.