We report the avalanche properties of InAs avalanche photodiodes (APDs), extracted from avalanche gain and excess noise measurements performed under pure electron and pure hole injections, and from Monte Carlo simulations. For a given avalanche width electron initiated gain was found to be significantly higher than conventional InP and Si APDs. Hole initiated multiplication was negligible confirming the electron only multiplication process within the field range covered. Excess noise measurements showed the excess noise factors of less than 2, providing further evidence of the ideal avalanche properties in InAs. Monte Carlo simulations performed provided good agreement to experimental results.