Metallurgical Behavior of Gold‐Based Ohmic Contacts to the InP / InGaAsP Material System

Abstract

The performance and reliability of semiconductor devices depend critically on the electrical quality and stability of the metal contacts. Gold‐based metallizations are generally used to form ohmic contacts and Schottky barriers to the III–V material systems. In this paper, we study the interfacial reaction of Be‐Au and Sn‐Au ohmic contact metallizations on normalInP , normalInGaAsP , and normalInGaAs . Staining, cathodoluminescence imaging, and x‐ray microanalysis are used to analyze the metallurgical interactions. Under typical alloying conditions for ohmic contact formation (420°C for 10 min), the depth of metal‐semiconductor interaction is found to depend on the amount of gold deposited. For the same thickness of contact metallization, this depth is largest for normalInGaAs , followed by normalInGaAsP and then normalInP . Analysis of normalInP/normalInGaAsP LED's shows that the 3 μm thick Sn‐Au n‐contact penetrates ∼3 μm into the normalInP window layer. The 2.9 kÅ thick Be‐Au p‐contact completely penetrates the contact layer which is typically 0.5 μm of normalInGaAsP false(λ=1.1 μnormalmfalse) or normalInGaAs false(λ=1.6 μnormalmfalse) .

Au - Be/Ru/Au multilayer metallization as a stable ohmic contact scheme to p-type InP

“…Evolved gas analysis (EGA) experiments showed that gold-based metallizations deposited on the surface of InP greatly enhance the thermal decomposition of the semiconductor, the total quantity of evolved phosphorus being roughly proportional to the quantity of gold (Mojzes et al 1986). Moreover, a strong tendency of Au to migrate in depth into the InP substrate during the alloying of contacts was also reported; it was found that the diffusion depth of Au is directly proportional to the thickness of gold-based contact layer (Camlibel et al 1982). Thus, a substantial reduction in the amount of Au available for reaction with the surface of the semiconductor is necessary for optimization of the contact properties.…”

The role of Ru in improving Au-Be ohmic contacts to p-type InP

“…To obtain ohmic properties and low specific contact resistance values, such contacts must be alloyed at temperatures of about 400-425OC. However, during this heat treatment of contacts, a strong metallurgical interaction between the Au, In and P takes place at the contact-semiconductor interface, especially when goldbased metallizations are evaporated in thick layers (6,7). As a result, non-planar spiking reaction fronts are formed with a deep protrusion of Au into the semiconductor, which can cause a degradation of contacts and device reliability problems (7).…”