GaN Fabrication

Fabrication of Low Resistance n- and p-contact for High Performance GaN HFET

Low contact resistance is an important aspect to achieve high performance GaN HFET. We have achieved ohmic contact for both n-contact and p-contact to fabricate a high performance HFET which shows very high current density. The n-contact was formed by depositing Si/Al/Ti/Au metal stack and p-contact formed with Ni/Au metal stack. Both contacts were annealed after deposition.

Fig 1: I-V characterization of fabricated p- (left) and n-contact (right) for GaN based HFET.

Fabrication of Transparent and Low Resistance p-contact for MC-LED

To fabricate a MC-LED, a transparent and low-resistance p-contact was fabricated using Ni/ITO stack. This contact was compared with other conventional p-contact like Ni/Au and ITO. Proposed Ni/ITO contact is not as good as Ni/Au in terms of resistivity, but it shows much higher transparency.

Fig 2: (left) I-V characterization comparison of fabricated different p-contact, (right) transparency comparison of the fabricated p-contacts.

Process Development and Fabrication of Dielectric Bragg Reflector

Process of fabricating dielectric Bragg reflector was developed as the first step of achieving first ever GaN based VCSEL. The Bragg reflector fabricated had controllable reflectivity with the variation of number of dielectric pairs. Our developed Bragg reflector had about 97% reflectivity with 8 pairs of dielectric layers.

Fig 3: Reflectivity of fabricated dielectric Bragg reflector with various number of pairs.